Preparation method and device based on cycloparaphenylene-metallocene catalyst and single-walled carbon nanotube of cycloparaphenylene-metallocene catalyst

Abstract

The invention relates to the technical field of preparation of carbon nanotube catalyst materials, in particular to a catalyst for a single-walled carbon nanotube of a chemical vapor deposition device, a preparation method of the catalyst, and a method and a special device for preparing the single-walled carbon nanotube by using the catalyst in an injection floating manner. The invention provides a novel solid precursor catalyst based on a host-guest compound. The catalyst can spontaneously form nano-metal active particles which are highly uniform in size and good in dispersity in a precursor cracking stage. The method is simple and controllable. The prepared single-walled carbon nanotube can realize ultra-narrow diameter distribution, and the diameter distribution range is less than or equal to 0.5 nm. And the high-yield, continuous or semi-continuous preparation of the single-walled carbon nanotubes is realized.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube catalyst material preparation technology, specifically to a catalyst for single-walled carbon nanotubes in a chemical vapor deposition apparatus, its preparation method, and a method and dedicated apparatus for preparing single-walled carbon nanotubes using the catalyst via floating catalysis. Background Technology

[0002] Single-walled carbon nanotubes (SUVs) have broad application prospects in nanoelectronic devices, composite materials, and energy storage due to their unique structure and excellent electrical, mechanical, and thermal properties. However, the core bottleneck for their large-scale, high-quality applications lies in the difficulty of preparing SUVs with uniform structure, especially narrow diameter and chirality.

[0003] Currently, the mainstream preparation method is chemical vapor deposition, mainly divided into substrate-supported method and floating catalyst method (FCCVD). Although the substrate-supported method can grow ordered arrays, the yield is limited by the substrate area, and the catalyst particles are prone to Ostwald ripening at high temperatures, resulting in a wider diameter distribution. The floating catalyst method can achieve high yield and continuous production, but the size of the metal catalyst particles that nucleate instantaneously during high-temperature pyrolysis of the liquid catalyst precursor is difficult to control, and they are prone to agglomeration. This results in a wide range of diameters for the grown single-walled carbon nanotubes, typically between 1.0 and 3.0 nm, and a mixture of semiconducting and metallic nanotubes.

[0004] In recent years, to precisely control catalyst size, some studies have proposed designing catalyst precursors using host-guest chemistry. For example, Chinese patent CN120922857A discloses the use of host-guest interactions between pillar aromatics and cyclopentadienyl metals to prepare uniformly sized nanocatalyst particles in situ on a substrate for the growth of single-walled carbon nanotubes. While this method can achieve precise control of catalyst size, it is essentially a substrate-based method, limiting yield and production continuity, and it does not address the stability issue of the catalyst at prolonged high temperatures. Other patents have attempted to use solid powder catalysts to replace liquid precursors to simplify the FCCVD process, but this approach lacks sufficient control over the initial size and dispersion of catalyst particles, resulting in limited improvement in product uniformity.

[0005] Therefore, the existing technology has the following shortcomings: the catalyst in the traditional floating catalyst method cannot float continuously and effectively during the growth and deposition process, resulting in the inability to control the catalyst nucleation and growth kinetics and a wide product diameter distribution; the substrate method based on the host and guest has low yield and is difficult to meet the needs of large-scale production; there is a lack of a solution that can combine the advantages of the precise control of the host and guest method and the high efficiency and continuity of the floating method. Summary of the Invention

[0006] This invention provides a novel floating catalyst based on a host-guest complex solid precursor. This catalyst can spontaneously form highly uniform and well-dispersed nano-sized metallic active particles during the precursor pyrolysis stage, overcoming the defect of wide diameter distribution of products in existing floating catalyst methods. A method for preparing the above catalyst is also provided; this method is simple, controllable, and enables large-scale synthesis of the host-guest complex. This invention also provides a method for preparing single-walled carbon nanotubes, which can achieve high-yield, continuous or semi-continuous preparation of single-walled carbon nanotubes, and the single-walled carbon nanotubes prepared using the above catalyst have a diameter distribution range ≤0.5 nm. This invention further provides a dedicated floating catalyst chemical vapor deposition apparatus suitable for the above methods, which enables stable, continuous, and controllable feeding of the solid catalyst precursor.

[0007] This invention provides a catalyst precursor based on cyclic [n]-p-phenylene-metallocene single-walled carbon nanotubes. The catalyst precursor is a host-guest complex microparticle, comprising a cyclic [n]-p-phenylene host molecule and a metallocene guest molecule, with a molar ratio of cyclic [n]-p-phenylene host molecule to metallocene guest molecule of 1:1-1:2. It is formed by molecular self-assembly and physical encapsulation of the cyclic [n]-p-phenylene host molecule, metallocene guest molecule, and optional growth promoter. The precursor is a solid powder with a particle size of 1-100 μm, exhibiting good flowability and thermal stability. A catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein the catalyst precursor further comprises a growth promoter at a mass fraction of 0.1%-5% of the catalyst precursor complex. A catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein the cyclo[n]-p-phenylene host molecule is a macrocyclic molecule with rigid cavities, such as cyclo[n]-p-phenylene or its derivatives, whose size can be perfectly matched with carbon nanotubes, graphene, fullerene, etc., where n is selected from any integer from 1 to 18; In some implementations, n is selected from any integer between 5 and 15; in other implementations, n is selected from 10 or 12. A catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein the metallocene guest molecule is an organometallic compound capable of preparing the host molecule cavity-encapsulated structure, and may be selected from one or more of ferrocene, cobalt cerocene, iron acetylacetonate, and cobalt acetylacetonate; A catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein the growth promoter is selected from thiophene, selenophene, or derivatives of thiophene or selenophene; This invention also provides a method for preparing a catalyst precursor based on cyclic [n]-p-phenylene-metallocene single-walled carbon nanotubes, comprising the following steps: (a) Dissolve the cyclo[n] p-phenylene host molecule and the metallocene guest molecule in a first organic solvent at a molar ratio of 1:1-1:2. Add the metallocene guest solution to the cyclo[n] p-phenylene host solution at 25-40℃ and stir continuously for 2-12 hours to fully encapsulate the cyclo[n] p-phenylene host molecule and the metallocene guest molecule to form a stable mixed solution. (b) Add a second organic solvent containing a growth promoter to the mixed solution obtained in step (a), or directly add a trace amount of poor liquid solvent, and react to form stable complex particles; (c) The composite particles obtained in step (b) are precipitated, separated, and dried to obtain a catalyst precursor with good flowability.

[0008] A method for preparing a catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein in step (a) the first organic solvent is selected from chloroform and dichloromethane; in step (b) the second solvent is selected from ethanol and acetonitrile, and the volume ratio of the second organic solvent to the first organic solvent is 3:1-10:1.

[0009] A method for preparing a catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, wherein in step (b), the separated composite particles are precipitated and washed 3-5 times with a poor solvent before drying; the poor solvent is selected from ethanol and acetonitrile; the drying is carried out in a vacuum drying oven at 40-60℃ for 6-12 hours. A method for preparing single-walled carbon nanotubes based on a cyclo[n]-p-phenylene-metallocene catalyst includes the following steps: (1) Preparation of catalyst precursor: The catalyst precursor was prepared according to the preparation method of the catalyst precursor based on cyclic [n] p-phenylene-metallocene single-walled carbon nanotubes described above; (2) Preparation of single-walled carbon nanotubes: In the chemical vapor deposition reaction system, the catalyst precursor prepared in step (1) is preheated at 300-600℃ in the preheating zone under vacuum to initially decompose and release metal species confined and protected by the host molecules. Then, in the presence of carbon source gas and carrier gas, it is heated at 1100-1400℃ in the main reaction zone to completely decompose the host molecules and form uniform nano-metal catalyst particles in situ (average particle size 1-3nm, size deviation ≤±15%). At this time, under the interaction of the carrier gas and carbon source gas, the nano-metal catalyst particles form a floating state, fully contact the carbon source gas and catalytically decompose to obtain single-walled carbon nanotubes.

[0010] A method for preparing single-walled carbon nanotubes based on a cyclo[n]-p-phenylene-metallocene catalyst, wherein the carbon source gas in step (2) is selected from one or more of ethylene, carbon monoxide, methane or ethanol; and the carrier gas is one of argon, nitrogen or hydrogen. A single-walled carbon nanotube is prepared using the method described above for preparing single-walled carbon nanotubes based on a cyclo[n]-p-phenylene-metallocene catalyst.

[0011] A single-walled carbon nanotube, wherein the diameter of the single-walled carbon nanotube is 0.5-2 nm; A single-walled carbon nanotube, wherein the diameter of the single-walled carbon nanotube is 1-2 nm; A single-walled carbon nanotube, wherein the diameter of the single-walled carbon nanotube is 1.0-1.75 nm; The present invention also discloses an apparatus for preparing single-walled carbon nanotubes, the apparatus comprising: a solid powder screw feeder system, a reaction system, a gas supply system, and a product collection system.

[0012] An apparatus for preparing single-walled carbon nanotubes, wherein the solid powder screw feeding system includes a hopper, a precision screw feeding device and a "coaxial gas sheath" gas-solid mixing chamber, for achieving precise, stable and continuous injection feeding of solid precursor powder, for precisely and continuously feeding the catalyst precursor into the reactor tube; The reaction system includes a furnace tube and a multi-temperature zone tube furnace. The multi-temperature zone tube furnace sequentially includes a preheating zone for cracking the catalyst precursor, a main reaction zone for growing single-walled carbon nanotubes, and a rapid cooling zone for terminating growth. The gas supply system includes independent carrier gas path and carbon source gas path. The carrier gas path is connected to the inner and outer pipes of the gas-solid mixing chamber of the "coaxial gas sheath" and is used to transport the precursor. The carbon source gas path is directly introduced into the main reaction zone. The gas supply system is mainly used to independently supply carrier gas and carbon source gas to the chemical vapor deposition reaction system. The product collection system is located at the end of the reaction tube and includes a water-cooled jacket and a filter equipped with a polycarbonate membrane or ceramic filter element. An apparatus for preparing single-walled carbon nanotubes, wherein the reaction tube in the main reaction zone of the reaction system is made of a high-temperature resistant composite material, which is selected from one of quartz tubes, silicon carbide tubes, and graphite tubes.

[0013] An apparatus for preparing single-walled carbon nanotubes, wherein the solid powder feeding system includes a hopper, a precision screw feeder, and a coaxial gas sheath device for gas-solid mixing and precursor injection.

[0014] An apparatus for preparing single-walled carbon nanotubes, wherein the precursor injection tube is located at the center of the furnace tube axis or at any position on the inner wall of the furnace tube, preferably at the center of the furnace tube axis.

[0015] An apparatus for preparing single-walled carbon nanotubes, wherein the number of precursor injection tubes is 1-12, preferably 1, 3 or 4.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The catalyst size is precisely controllable. By utilizing the molecular-level confinement effect of the [n] ring-p-phenylene cavity on the organometallic guest, the migration and aggregation of metal species are effectively suppressed during pyrolysis, thereby forming highly uniform and well-dispersed nanocatalyst particles in situ. This is the fundamental guarantee for achieving a narrow diameter distribution of single-walled carbon nanotubes.

[0017] 2. The product quality is excellent. The single-walled carbon nanotubes prepared using this invention have a concentrated diameter distribution. Figure 3 Analysis shows that products with an average diameter in the range of 1.2 ± 0.25 nm can be stably obtained, exhibiting high semiconductor performance, few defects, and good crystallinity.

[0018] 3. The process is continuous and has a high yield. It adopts the advantages of continuous feeding and continuous production using the injection floating catalyst method, avoiding the limitations of batch production in the substrate method. The solid powder feeding method is stable and controllable, not prone to clogging, and suitable for scale-up production. The yield per unit time can be increased by more than 45% compared with traditional solution-fed FCCVD.

[0019] 4. The precursor is stable and easy to store and transport. Compared with the traditional ferrocene / thiophene solution, the solid powder form of the precursor is chemically stable, does not easily volatilize or decompose, and is safer and more convenient to store and transport.

[0020] 5. The device is highly specialized. The "screw feed + coaxial gas sheath" feeding system designed for solid powder catalysts solves the problem that traditional FCCVD devices can only process liquid or gaseous precursors, providing a hardware foundation for the application of new catalyst systems. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a scanning electron microscope (TEM) image of the single-walled carbon nanotubes prepared in Example 1 of the present invention; Figure 2This is a transmission electron microscope (SEM) image of the single-walled carbon nanotubes prepared in Example 1 of the present invention; Figure 3 This is a statistical histogram of the diameter distribution of single-walled carbon nanotubes prepared in Example 1 of the present invention; Figure 4 This is a schematic diagram of the floating catalyst chemical vapor deposition apparatus of the present invention, wherein 1-screw feeder, 2-buffer bin, 3-coaxial gas sheath device, 4-furnace tube sealing end cap, carbon source gas inlet pipe, 6-catalyst injection pipe, 7-furnace body, 8-furnace tube, 9-collection bin, 10-filter screen, 11-tail gas pipe.

[0024] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0026] Example 1 Cyclic

[10] p-Phenylenol-ferrocene composite precursor and its preparation of single-walled carbon nanotubes Step 1: Precursor preparation. Weigh 199 mg (host) of cyclo

[10] -p-phenylene and dissolve it in 20 ml of chloroform. Weigh 30 mg of ferrocene (guest, host-guest molar ratio 1:1.2) and dissolve it in 5 ml of chloroform. Under magnetic stirring, slowly add the ferrocene solution to the cyclo

[10] -p-phenylene solution. After the addition is complete, continue stirring at 30°C for 6 hours. Then, slowly add 100 ml of ethanol (a poor solvent) to the mixture, and a large amount of light yellow flocculent precipitate immediately appears. After stirring for another hour, filter using a microporous membrane, and wash the obtained solid three times with ethanol. Place the filter cake in a vacuum drying oven at 50°C and dry for 10 hours. After grinding, obtain a free-flowing yellow solid powder (labeled as precursor A).

[0027] Step 2, preparation of single-walled carbon nanotubes, using... Figure 4In the apparatus shown, 1.0 g of precursor A was weighed and placed into the hopper of the solid powder feeder. The furnace tube 8 was evacuated and purged with argon. The main reaction section temperature was set to 1200℃, and the preheating section temperature was set to 450℃. The screw feeder 1 added the precursor to the buffer chamber 2 at a rate of approximately 0.5 g / h. Argon was used as the carrier gas at a flow rate of 500 sccm, and the coaxial gas sheath device 3 formed a high-speed carrier gas, carrying the precursor powder and injecting it into the preheating section at a rate of approximately 0.5 g / h. Simultaneously, ethylene (carbon source gas) at a flow rate of 50 sccm and hydrogen at a flow rate of 150 sccm were introduced into the main reaction section. The reaction continued for 2 hours. Dense black flocculent products were collected on the filter membrane 10 of the receiving chamber 9 at the end of the reaction tube.

[0028] Step 3: Product characterization and TEM observation. Figure 1 The product was found to be pure single-walled carbon nanotube bundles, without obvious amorphous carbon or metal particle impurities. The diameter of 100 individual tubes was randomly measured, and the average diameter was found to be 1.35 nm with a standard deviation of 0.18 nm. The diameter distribution ranged from 1.0 to 1.75 nm, showing a narrow distribution characteristic.

[0029] Example 2 Cyclic

[12] p-Phenylenylacetylacetone cobalt complex precursor and its preparation of single-walled carbon nanotubes Step 1, precursor preparation: Following the method in Example 1, the host was replaced with cyclo

[12] -p-phenylene, and the guest was replaced with cobalt acetylacetonate, with a host-guest molar ratio of 1:1.5. Before the complex precipitates, 5 mg of thiophene is added to the mixture as a growth promoter. Finally, a dark green solid powder (labeled as precursor B) is obtained.

[0030] Step 2: Preparation of single-walled carbon nanotubes. The process conditions are the same as in Example 1, except that precursor A is replaced with precursor B, the main reaction temperature is adjusted to 1180℃, the carbon source is carbon monoxide, and the flow rate is 100 sccm. The product is collected after the reaction.

[0031] Step 3, Product Characterization TEM and Raman spectroscopy analysis showed that the average diameter of the obtained single-walled carbon nanotubes was 1.05 nm with a standard deviation of 0.15 nm.

[0032] Comparative Example: Traditional Solution-Based FCCVD An ethanol solution containing 0.1 wt% ferrocene and 0.05 wt% thiophene was prepared as a catalyst precursor using conventional methods. Using the same apparatus, but with a liquid injection pump for feeding, ethylene was used as the carbon source, and the experiment was conducted at a reaction temperature of 1200 °C. TEM analysis of the obtained single-walled carbon nanotubes showed that their diameter ranged from 0.8 to 2.5 nm, with an average diameter of 1.5 nm.

[0033] The above are only some embodiments of this application and do not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the content of this application specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, characterized in that, The catalyst precursor comprises a cyclo[n]-p-phenylene host molecule and a metallocene guest molecule, wherein the molar ratio of the cyclo[n]-p-phenylene host molecule to the metallocene guest molecule is 1:1 to 1:

2.

2. The catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes according to claim 1, characterized in that, The catalyst precursor further comprises a growth promoter, which is at least one of thiophene, selenophene, or a derivative thereof, and its mass fraction in the catalyst precursor is 0.1%-5%.

3. The catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes according to claim 1, characterized in that, The cyclo[n]-p-phenylene host molecule is selected from cyclo[n]-p-phenylene or its derivatives, wherein n is selected from any integer from 1 to 18, preferably n is 10 or 12.

4. The catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes according to claim 1, characterized in that, The metallocene guest molecule is selected from one or more of ferrocene, cobalt cerone, iron acetylacetonate, and cobalt acetylacetonate.

5. A method for preparing a catalyst precursor based on cyclo[n]-p-phenylene-metallocene single-walled carbon nanotubes, characterized in that, Includes the following steps: (a) Dissolve the cyclo[n] p-phenylene host molecule and the metallocene guest molecule in a first organic solvent at a molar ratio of 1:1-1:

2. Add the metallocene guest solution to the cyclo[n] p-phenylene host solution at 25-40℃ and stir continuously for 2-12 hours to form a mixed solution. (b) Add a second organic solvent containing a growth promoter, or a poor solvent, to the mixed solution obtained in step (a) to react and form stable complex particles; (c) The composite particles obtained in step (b) are precipitated, separated, and dried to obtain the catalyst precursor.

6. The preparation method according to claim 5, characterized in that, In step (a), the first organic solvent is selected from chloroform and dichloromethane; in step (b), the second solvent is selected from ethanol and acetonitrile; the volume ratio of the second organic solvent to the first organic solvent is 3:1-10:

1.

7. The preparation method according to claim 5, characterized in that, In step (b), the separated composite particles are washed 3-5 times with a poor solvent before drying; the poor solvent is selected from ethanol and acetonitrile; the drying is carried out in a vacuum drying oven at 40-60℃ for 6-12 hours.

8. A method for preparing single-walled carbon nanotubes based on a cyclo[n]-p-phenylene-metallocene catalyst, characterized in that, Includes the following steps: (1) Preparation of catalyst precursor: The catalyst precursor is prepared according to the preparation method described in claims 5-7; (2) Preparation of single-walled carbon nanotubes: In a chemical vapor deposition reaction system, the catalyst precursor prepared in step (1) is preheated at 300-600℃ in a vacuum environment, and then heated at 1100-1400℃ in the presence of carbon source gas and carrier gas to obtain single-walled carbon nanotubes.

9. The preparation method according to claim 8, characterized in that, The carbon source gas in step (b) is selected from one or more of ethylene, carbon monoxide, methane or ethanol; the carrier gas is selected from one of hydrogen, argon and nitrogen.

10. A method for preparing single-walled carbon nanotubes based on a cyclo[n]-p-phenylene-metallocene catalyst, characterized in that, The diameter of the single-walled carbon nanotubes is 0.5-2 nm.

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