A method and apparatus for preparing high-quality single-walled carbon nanotubes

Abstract

This application provides a method and apparatus for preparing high-quality single-walled carbon nanotubes. A dispersion of liquid carbon source, iron source, co-catalyst, and a small amount of water is introduced from the top of a high-temperature furnace, while reducing gas and protective gas are simultaneously introduced. Crude single-walled carbon nanotubes are synthesized via a floating catalytic method, and the crude product is deposited in the lower part of the high-temperature furnace and inside a collection tank. The crude product is then subjected to multiple high-temperature calcinations and strong acid treatments to remove metallic impurities. This application innovatively adjusts the temperature of the upper and lower sections of the furnace, lowering the temperatures in the first and third temperature zones to avoid product quality deterioration and carbon nanotube conversion. Controlling the first and second temperature zones and the collection tank prevents excessively high temperatures that could cause carbon nanotube burning while promoting deposition. Heating the collection tank to a certain temperature further facilitates carbon nanotube deposition, increasing carbon nanotube yield. The preparation method and apparatus of this application improve the yield and quality of single-walled carbon nanotubes.

Description

Technical Field

[0001] This application belongs to the field of single-walled carbon nanotube material technology, and particularly relates to a method and apparatus for preparing high-quality single-walled carbon nanotubes. Background Technology

[0002] Single-walled carbon nanotubes (SUVs) are helical structures composed of a single layer of carbon atoms. They possess characteristics such as light weight, high pressure resistance, high temperature resistance, high wear resistance, high aspect ratio, high modulus, and high strength. They can be used to modify metallic and polymeric materials to achieve the goal of preparing high-strength, lightning-resistant, stealthy, and low-temperature-resistant anti-icing materials. Common synthesis methods for SUVs include laser evaporation, arc evaporation, and chemical vapor deposition. Compared to multi-walled carbon nanotubes, SUVs have a wide range of applications due to their unique physical properties. In the field of achieving lightning protection, the maximum current density of SUVs can reach 1*10⁻⁶. 9 A / cm 2 In terms of enhancing the mechanical properties of materials, single-walled carbon nanotubes (SUVs) have a tensile strength greater than 20 GPa, while multi-walled carbon nanotubes (MWCs) have a tensile strength greater than 11 GPa. The thermal conductivity of SUVs ranges from 3270 to 9800 W / m K, while that of MWCs is only 830 to 3000 W / m K. In the fabrication of electronic devices, the capacitance of SUVs is typically 180 F / g, higher than that of MWCs. Furthermore, SUV capacitors can achieve a power density of up to 20 kW / kg and an energy density of up to 7 Wh / kg. In the biomedical field, SUVs and MWCs have different effects on bacterial drug resistance. SUVs can severely disrupt the cell walls of bacteria such as E. coli, leading to their death, which is very helpful in addressing bacterial drug resistance.

[0003] Laser evaporation is an effective method for preparing single-walled carbon nanotubes. First, a carbon source material (such as graphite) is placed in a high-temperature environment to reach its evaporation temperature. Then, a powerful laser beam is used to instantaneously heat the carbon source, causing it to evaporate and form soot. Under laser radiation, the soot particles undergo localized heating and cooling processes. This heating and cooling results in localized high-temperature and low-temperature regions within the soot particles. In the high-temperature regions, carbon atoms rearrange and recombine to form the core of the carbon nanotube. However, laser evaporation suffers from high cost, difficulty in control, and challenges in large-scale industrialization. The high cost of laser equipment and related equipment increases the cost of the prepared materials. Laser evaporation requires precise control of parameters such as laser power and evaporation rate, which places high demands on equipment and operators, potentially leading to instability in the preparation process. Furthermore, laser evaporation is typically suitable for small-scale preparation, and large-scale industrialization remains challenging.

[0004] Arc discharge is a commonly used method for producing carbon nanotubes. This method involves applying a high voltage and current between two electrodes in a vacuum or inert gas environment to create an electric arc. This process causes the temperature in the electrode region to rise to very high levels. Due to the high temperature, the graphite electrodes evaporate, forming carbon atom clusters. Under the high temperature and high energy environment, these carbon atom clusters rearrange and restructure to form carbon nanotubes. These carbon nanotubes are sputtered from the arc region and collected. However, the arc method is costly, produces many impurities, and is difficult to control. The arc method requires high-voltage and high-current equipment, which is expensive and consumes a lot of energy, increasing the overall production cost. Materials prepared by the arc method may be contaminated by impurities generated during the arc discharge, affecting the quality and performance of the material. Furthermore, the arc discharge process is affected by various factors, making precise control difficult and leading to unstable quality of the prepared materials.

[0005] Chemical vapor deposition (CVD) is a method that uses a metal catalyst to deposit a desired thin film material onto a substrate or furnace tube surface through a chemical reaction involving the introduction of precursor substances under specific atmospheric conditions. Specifically, metal catalysts such as nickel or iron are commonly used to promote the conversion of the carbon source gas during the deposition process. First, metal catalyst particles are deposited on the substrate or furnace tube surface. Then, the carbon source gas is introduced into the reaction chamber and decomposed. Under the action of the metal catalyst, the generated carbon molecules are adsorbed, thereby forming single-walled carbon nanotubes. This method can efficiently prepare carbon nanotubes and has broad application prospects. However, CVD has stricter temperature requirements. Existing single-walled nanotube preparation techniques strive for temperature uniformity in the reactor, which may lead to non-uniformity and lattice defects in the material, affecting its properties. The purpose of this application is to explore a method and apparatus for preparing high-quality single-walled carbon nanotubes. Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to provide a method and apparatus for preparing single-walled carbon nanotubes that avoids the deterioration of product quality and the conversion of carbon nanotubes in a high-temperature furnace and improves product quality.

[0007] The first aspect of this application provides a method for preparing high-quality single-walled carbon nanotubes, comprising the following steps:

[0008] 1) Prepare a mixture of liquid carbon source, iron source, co-catalyst and a small amount of water, and make it into a dispersion;

[0009] 2) The dispersion is introduced from the top of the high-temperature furnace at a certain injection speed, while reducing gas and protective gas are introduced at the same time. The crude product of single-walled carbon nanotubes is synthesized by floating catalysis. The crude product is deposited in the lower part of the high-temperature furnace and the inside of the collection tank.

[0010] 3) Remove the crude product and purify it.

[0011] The purification process specifically includes continuous calcination at high temperature for a period of time to remove amorphous carbon from the surface; purification of the crude product by stirring with strong acid at room temperature; and repeating the above purification process to remove metallic impurities from the crude product.

[0012] In any embodiment, the furnace tube of the high-temperature furnace is provided with a first temperature zone, a second temperature zone, and a third temperature zone from the injection end to the collection tank end, and the temperature of the second temperature zone in the middle is greater than the temperature of the first and third temperature zones at both ends and the temperature of the collection tank.

[0013] In any embodiment, the temperature of the second temperature zone in the middle of the high-temperature furnace is 1000-1300℃, and the temperature of the first and third temperature zones at both ends of the high-temperature furnace is 500-600℃.

[0014] In any embodiment, the temperature of the collection tank is 500°C-600°C.

[0015] In any embodiment, the liquid carbon source is one or more of toluene, benzyl alcohol, or phenol; the iron source is one or more of ferric citrate, ferric nitrate, and ferric acetate; the co-catalyst is a sulfur source, which is one or more of thiophenol, selenophenol, and diethyl sulfide; the reducing gas is hydrogen sulfide, hydrogen, carbon monoxide, or methane; and the protective gas is an inert gas.

[0016] In any embodiment, the ratio of the iron source, liquid carbon source and co-catalyst is 1g:40-60mL:8mL; the ratio of the reducing gas to the protective gas is 800-2000:640-1600.

[0017] In any embodiment, the injection rate is 160-190 μL / min; the calcination conditions are air oxidation at 450-500°C for 1-1.5 h.

[0018] In any embodiment, the strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and aqua regia, and the stirring time during the purification process is 3-5 hours. The temperature is 20-25°C.

[0019] A second aspect of this application also provides an apparatus for preparing high-quality single-walled carbon nanotubes, including a high-temperature furnace, an injection nozzle, a receiving tank, a speed-controlled infusion device, and a gas source cylinder. The high-temperature furnace has a furnace tube running through its center. The injection nozzle is connected to the upper end of the furnace tube, and the receiving tank is connected to the lower end of the furnace tube. The furnace tube has a first temperature zone, a second temperature zone, and a third temperature zone from top to bottom. The second temperature zone has a heated furnace chamber. The gas source cylinder and the speed-controlled infusion device are both connected to the injection nozzle pipeline. The gas source cylinder includes a carbon source cylinder and a reducing gas cylinder.

[0020] In any embodiment, the receiving tank is equipped with a heater.

[0021] In any embodiment, the front end of the injection nozzle is a flared shape.

[0022] In any embodiment, the furnace tube is 1m long and has an inner diameter of 60-100mm. The ratio of the furnace tube lengths in the first temperature zone, the second temperature zone, and the third temperature zone is 1:2:1.

[0023] The beneficial effects of this invention are as follows: This application creatively divides the temperature in the single-walled carbon nanotube preparation reactor into different temperature zones—a first temperature zone, a second temperature zone, and a third temperature zone—by adjusting the temperature of the upper and lower sections of the furnace. By lowering the temperature of the first and third temperature zones, the deterioration of product quality and the conversion of carbon nanotubes are avoided. Furthermore, the first and second temperature zones, as well as the collection tank, are controlled at 500℃-600℃, which avoids carbon nanotube burning due to excessive temperature and promotes carbon nanotube deposition. Heating the collection tank at a certain temperature is also beneficial for carbon nanotube deposition, thereby increasing the yield of carbon nanotubes. The preparation method and apparatus of this application improve the yield and quality of single-walled carbon nanotubes. Attached Figure Description

[0024] Figure 1 This is a diagram of the apparatus for preparing single-walled carbon nanotubes using the bottom-feed floating catalytic method of this application;

[0025] Figure 2 This is a scanning electron microscope image of the product of Embodiment 1 of this application;

[0026] Figure 3 This is the Raman spectrum of the product in Example 1 of this application;

[0027] Figure 4 This is a scanning electron microscope image of the product in Embodiment 2 of this application;

[0028] Figure 5 This is the Raman spectrum of the product in Example 2 of this application;

[0029] Figure 6 This is a scanning electron microscope image of the product of Embodiment 3 of this application;

[0030] Figure 7 This is the Raman spectrum of the product in Example 3 of this application;

[0031] Figure 8 The image is a scanning electron microscope (SEM) image of the product at 200 nm in Comparative Example 1.

[0032] Figure 9 This is a scanning electron microscope image of the 1μm sample of Comparative Example 1.

[0033] Figure 10 The Raman spectrum of the product in Comparative Example 1;

[0034] Figure 11 Here is a scanning electron microscope image of the product at 200 nm, which is Comparative Example 2.

[0035] Figure 12 Here is a scanning electron microscope image of the 1μm sample of product 2 (Comparative Example 2);

[0036] Figure 13 The image shows the Raman spectrum of the product in Comparative Example 2.

[0037] Explanation of reference numerals in the attached figures:

[0038] High-temperature furnace 1; furnace tube 11; first temperature zone CO1; second temperature zone CO2; third temperature zone CO3; furnace chamber 12; injection nozzle 2; bell mouth 21; receiving tank 3; heater 31; speed-controlled infusion device 4; gas source cylinder 5; carbon source cylinder 51; reducing gas cylinder 52. Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the method for preparing high-quality single-walled carbon nanotubes according to this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0040] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0043] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0044] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0045] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] A method for preparing high-quality single-walled carbon nanotubes includes the following steps:

[0047] 1) Prepare a mixture of liquid carbon source, iron source, co-catalyst and a small amount of water, and make it into a dispersion;

[0048] 2) The dispersion is introduced from the top of the high-temperature furnace at a certain injection speed, while reducing gas and protective gas are introduced at the same time. The crude product of single-walled carbon nanotubes is synthesized by floating catalysis. The crude product is deposited in the lower part of the high-temperature furnace and the inside of the collection tank.

[0049] 3) Take out the crude product and calcine it under high temperature for a period of time to remove the amorphous carbon on the surface;

[0050] 4) Purify the crude product by stirring with a strong acid at room temperature;

[0051] 5) Repeat steps 3) and 4) to remove metallic impurities from the crude product.

[0052] The furnace tube of the high-temperature furnace is provided with three temperature zones from the injection end to the collection tank end: a first temperature zone, a second temperature zone, and a third temperature zone. The temperature of the second temperature zone in the middle is higher than that of the first and third temperature zones at both ends.

[0053] The temperature of the second temperature zone in the middle of the high-temperature furnace is 1000-1300℃, and the temperature of the first and third temperature zones at both ends of the high-temperature furnace is 500-600℃.

[0054] The temperature of the collection tank is 500℃-600℃.

[0055] In some embodiments, the liquid carbon source is one or more of toluene, benzyl alcohol, or phenol.

[0056] Toluene, benzyl alcohol, or phenol were chosen to prepare single-walled carbon nanotubes because they provide a high carbon source content as benzene rings, and have high stability and solubility. They can remain undecomposed under high temperature conditions and mix thoroughly with carbon precursors. Furthermore, they have good solubility for iron sources, demonstrating a strong ability to dissolve iron sources.

[0057] In some embodiments, the iron source is one or more of ferric citrate, ferric nitrate, and ferric acetate.

[0058] Ferric citrate (FeC6H5O7) exhibits high solubility and stability in the preparation of carbon nanotubes; ferric nitrate (Fe(NO3)3) also shows good solubility and reactivity in the preparation of carbon nanotubes; ferric acetate (Fe(C2H3O2)2) has high solubility in solution; ferric citrate, ferric nitrate, or ferric acetate have good solubility, stability, or reactivity, and can be used to synthesize single-walled carbon nanotubes through chemical vapor deposition, chemical reduction, or thermal decomposition.

[0059] In some embodiments, the co-catalyst is a sulfur source, which is one or more of thiophenol, selenol, and ethyl sulfide.

[0060] Sulfur sources are used as co-catalysts, while thiophenol, selenol, and diethyl sulfide are used as sulfur sources for the preparation of single-walled carbon nanotubes. Sulfur and selenium are located closer to oxygen in the periodic table, so they can play an etching role in the preparation of carbon nanotubes. This etching effect can reduce the content of amorphous carbon in the product, thereby improving the quality of carbon nanotubes.

[0061] Thiophenols and selenophenols can embed sulfur atoms into the structure of carbon nanotubes through pyrolysis, exhibiting high solubility and reactivity. Selenophenols can also act as co-catalysts during synthesis, promoting the growth of carbon nanotubes. This makes thiophenols and selenophenols commonly used sulfur sources.

[0062] Diethyl sulfide, as a sulfur-containing organic compound, can also provide sulfur atoms for the growth of carbon nanotubes. Under appropriate experimental conditions, ethyl sulfide can release sulfur atoms through pyrolysis and embed them into the structure of carbon nanotubes.

[0063] In some embodiments, the ratio of the iron source, liquid carbon source and co-catalyst is 1g:40-60mL:8mL.

[0064] Determining the amounts of iron source, liquid carbon source, and co-catalyst is crucial.

[0065] An excess of carbon source may cause overfilling of the active sites of the catalyst, thereby increasing the reaction rate and making the reaction too fast and difficult to control; an excess of sulfur source may also cause it to undergo an irreversible chemical reaction with the catalyst, poisoning the catalyst and causing it to lose its activity, reducing the reaction efficiency or completely inhibiting the reaction.

[0066] Sulfur sources act as promoters in some catalytic reactions. When the sulfur source is too high, the rate of the catalytic reaction may decrease, leading to slow reaction progress. Product selectivity decreases: Sulfur sources can regulate the selectivity of products in some reactions. When the sulfur source is insufficient, it may lead to a decrease in product selectivity and the generation of unexpected byproducts. During the reaction, sulfur sources can protect the catalyst from the influence of undesirable reactants. When the sulfur source is too high, the catalyst may be corroded or deactivated by undesirable reactants, thereby affecting the catalyst's effectiveness and stability.

[0067] The solubility of iron source catalysts in liquid carbon source solvents is limited. If too much is added, the iron source catalyst cannot be completely dissolved or even dispersed evenly. On the one hand, this will cause blockage of the liquid inlet pipe, making experiments impossible, and on the other hand, it will lead to waste of raw materials.

[0068] When a liquid carbon source comes into contact with an iron source catalyst, carbon nanotubes are grown on iron atom clusters. If the iron source is insufficient, the yield of carbon nanotubes will be affected.

[0069] In some embodiments, the reducing gas is hydrogen sulfide (H2S), hydrogen (H2), carbon monoxide (CO), or methane (CH4). Carbon monoxide is preferred as the reducing gas.

[0070] The primary function of introducing reducing gas is to control the growth mode and quantity of carbon nanotubes. Specifically, the reducing gas participates in the carbon nanotube growth reaction, influencing the diameter, length, and structural properties of the carbon nanotubes by providing a carbon source and adjusting reaction conditions. The reducing gas reacts with carbon precursors at high temperatures to generate active carbon species, which then participate in the carbon nanotube growth process. The diameter and quantity of carbon nanotubes can be controlled by adjusting parameters such as the flow rate, temperature, and pressure of the reducing gas. Furthermore, the reducing gas also cleans the catalyst surface, removing residual impurities and oxides, thereby improving the purity, crystallinity, and quality of the carbon nanotubes.

[0071] In some embodiments, the protective gas is an inert gas. This application uses nitrogen.

[0072] Nitrogen gas is characterized by high stability and low chemical reactivity, and it does not easily react with impurities or materials in carbon nanotubes, thus effectively protecting the structure and properties of carbon nanotubes.

[0073] Argon, helium, and other inert gases can also be used as protective gases. The choice of different inert gases should be based on the actual application requirements and specific conditions. For example, helium may be more suitable for cooling carbon nanotubes to reduce temperature-related problems. The main purpose of using inert gases is to prevent carbon nanotubes from undergoing oxidation and thermal decomposition reactions at high temperatures.

[0074] In some embodiments, the ratio of reducing gas to protective gas is 800-2000 sccm: 640-1600 sccm.

[0075] The ratio of reducing gas to protective gas is 800-2000 sccm : 640-1600 sccm, with a usage ratio of 5:4. If the ratio is too high, the gas linear velocity will be too fast, resulting in too short a gas retention time inside the furnace tube, causing the single-walled carbon nanotubes to deposit at the bottom of the furnace tube and in the collection tank before they have fully grown. If the ratio is too low, the single-walled carbon nanotubes will be burned in the high-temperature zone after full growth, resulting in an overly brittle and hard product, thus reducing the overall quality and grade of the product.

[0076] In some embodiments, the injection rate is 160-190 μL / min.

[0077] An excessively fast feed rate leads to rapid growth of single-walled carbon nanotubes (SUVs), while also increasing defects and the content of amorphous carbon. Conversely, a slow feed rate, while maintaining the quality of SUVs, results in low product quality, hindering large-scale industrial production.

[0078] In some embodiments, the calcination conditions are air oxidation at 450-500°C for 1-1.5 hours.

[0079] The purpose of calcination is to remove excess amorphous carbon. High-temperature treatment causes the amorphous carbon to undergo a combustion reaction, further purifying the product. During calcination, oxygen is used as the oxidant to promote the combustion reaction of the amorphous carbon, which helps purify the product. The calcination time is shortened to 1-1.5 hours (excluding heating and cooling time) compared to existing experimental procedures, with a heating rate of 5℃ / min, ensuring that calcination is carried out within an appropriate temperature and time range to fully utilize the purification effect. This reduces the oxidation of carbon nanotubes and lowers time costs.

[0080] In some embodiments, the strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and aqua regia, and the stirring time of the purification process is 3-5 hours. The temperature is 20-25°C.

[0081] Acids are used to remove amorphous carbon; concentrated hydrochloric acid, concentrated sulfuric acid, or aqua regia, or a combination thereof, can be selected. The use of acid can further remove residual iron and helps improve the purity of single-walled carbon nanotubes. The calcination and acid washing processes are interconnected and interact. By shortening the air oxidation time and extending the high-temperature stirring time, excessive oxidation of single-walled carbon nanotubes can be prevented, thus avoiding a severe decline in the quality of the carbon nanotubes.

[0082] In some embodiments, the calcination and purification process is repeated 3-5 times to remove more iron from the single-walled carbon nanotubes. If a single calcination is too long, the internal structure of the carbon nanotubes will change, causing them to lose their original morphology and properties. Multiple short calcinations allow for gentler heating conditions during both heating and cooling, avoiding the yield reduction caused by excessively long heating times or high temperatures in traditional methods.

[0083] like Figure 1 As shown, an apparatus for preparing high-quality single-walled carbon nanotubes includes a high-temperature furnace 1, an injection nozzle 2, a receiving tank 3, a speed-controlled infusion device 4, and a gas source cylinder 5. The high-temperature furnace 1 has a furnace tube 11 running through its center. The injection nozzle 2 is connected to the upper end of the furnace tube 11, and the receiving tank 3 is connected to the lower end of the furnace tube 11. The furnace tube 11 has a first temperature zone CO1, a second temperature zone CO2, and a third temperature zone CO3 from top to bottom. The second temperature zone CO2 has a heated furnace chamber 12. The gas source cylinder 5 and the speed-controlled infusion device 4 are both connected to the injection nozzle 2 via pipelines. The gas source cylinder 5 includes a carbon source cylinder 51 and a reducing gas cylinder 52.

[0084] The receiving tank 3 is equipped with a heater 31.

[0085] The front end of the injection nozzle 2 is a flared mouth 21.

[0086] The length of the furnace tube 11 is 1-3m, preferably 1m, and the inner diameter of the furnace tube 11 is 60-100mm. The length ratio of the furnace tube 11 in the first temperature zone CO1, the second temperature zone CO2 and the third temperature zone CO3 is 1:2:1 to 1:3:1, with a preferred ratio of 1:2:1.

[0087] The design of the furnace tube length parameters in this application is beneficial to improving the yield and quality of carbon tubes.

[0088] The dispersion required for single-walled carbon nanotube (SCH) preparation is introduced into the vertical tubular high-temperature furnace via a speed-controlled infusion device under the influence of gases from the carbon source and reducing gas cylinders. The flared nozzle of the injection head prevents gas and liquid from flowing back to the top of the first temperature zone, thus avoiding insufficient growth and deposition temperatures for SCH. The high-temperature furnace provides additional heating to the second temperature zone to achieve the required growth temperature of 1000-1300℃ for SCH. However, the first temperature zone, where the dispersion evaporates and sublimates, and the third temperature zone, where SCH deposits, have significantly lower temperatures than the second temperature zone. Conversely, excessively low temperatures in the first and third temperature zones severely impact SCH growth. Therefore, after optimization, the temperatures in the first and third temperature zones can be controlled between 500-600℃. The receiving tank is primarily used to collect the crude SCH product. Single-walled carbon nanotubes (SWC nanotubes) are deposited only in the first and third temperature zones and inside the receiving tank 7. The second temperature zone is used to provide the growth temperature for SWC nanotubes but does not perform deposition; excessively high temperatures would cause the generated SWC nanotubes to transform into other carbon materials such as graphite, fullerenes, and carbon black. The receiving tank is mainly used to collect excess SWC nanotubes. The heater is used to ensure that the receiving tank meets the deposition temperature of 500-600℃ for SWC nanotubes.

[0089] Example

[0090] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0091] Example 1

[0092] Crude single-walled carbon nanotubes were synthesized from 10 g of ferric citrate and 8 mL of thiophenol in 600 mL of toluene using a floating catalytic method at a temperature of 1000℃, with simultaneous introduction of 1000 sccm of nitrogen and 800 sccm of carbon monoxide, and a liquid injection rate of 160 μL / min. Figure 1In the single-walled carbon nanotube (SWC) preparation apparatus shown, the first and third temperature zones were set at 500°C, and the second temperature zone was set at 1300°C. The collection tank temperature was 500°C. Subsequently, the crude product was purified. First, it was calcined at 450°C with oxygen for 2 hours to remove amorphous carbon from the surface. Then, it was treated with 3M aqua regia at 25°C with stirring for 3 hours to remove metallic impurities. To obtain purer SWC nanotubes, the purification steps were repeated three times. After purification, SWC nanotubes were obtained. Scanning electron microscopy (SEM) morphology analysis confirmed that the product was indeed SWC nanotubes. Weighing and Raman spectroscopy revealed that within the reaction zone of a 60mm diameter, 1.5m high furnace tube, 0.4568g of purified SWC nanotubes could be produced in 3 hours, with a Raman G / D ratio as high as 205.9. Figure 2 , 3 As shown.

[0093] Example 2

[0094] Crude single-walled carbon nanotubes were synthesized from a 400 mL benzyl alcohol solution containing 10 g ferric nitrate and 8 mL thiophenol using a floating catalytic method at a temperature of 1200 °C, with simultaneous introduction of 1000 sccm of nitrogen and 800 sccm of carbon monoxide, and a liquid injection rate of 160 μL / min. Figure 1 In the single-walled carbon nanotube (SWC) preparation apparatus shown, the first and third temperature zones were set at 500°C, and the second temperature zone at 1000°C. The collection tank temperature was 600°C. Subsequently, the crude product was purified. First, it was calcined with oxygen at 450°C for 1 hour to remove amorphous carbon from the surface. Then, it was treated with 3M aqua regia at 25°C with stirring for 3 hours to remove metallic impurities. To obtain purer SWC nanotubes, the purification steps were repeated three times. After purification, SWC nanotubes were obtained. Scanning electron microscopy (SEM) morphology analysis confirmed that the product was indeed SWC nanotubes. Weighing and Raman spectroscopy revealed that within the reaction zone of a 60mm diameter, 1.5m high furnace tube, 0.4237g of purified SWC nanotubes could be produced in 3 hours, with a Raman G / D ratio as high as 149.9. Figure 4 , 5 As shown.

[0095] Example 3

[0096] Crude single-walled carbon nanotubes were synthesized from 10 g of ferric sulfate and 8 mL of selenophenol in a 600 mL phenol solution at 1300 °C with 1000 sccm of nitrogen and 800 sccm of carbon monoxide peroxide atmosphere using a floating catalytic method. Figure 1In the single-walled carbon nanotube (SWC) preparation apparatus shown, the first and third temperature zones were set at 600°C, and the second temperature zone was set at 1300°C. The collection tank temperature was 600°C. Subsequently, the crude product was purified. First, it was calcined at 500°C with oxygen for 1.5 hours to remove amorphous carbon from the surface. Then, it was stirred with 3M concentrated hydrochloric acid at 20°C for 3 hours to remove metallic impurities. To obtain purer SWC nanotubes, the purification steps were repeated three times. After purification, SWC nanotubes were obtained. Scanning electron microscopy (SEM) morphology analysis confirmed that the product was indeed SWC nanotubes. Weighing and Raman spectroscopy revealed that within the reaction zone of a 60mm diameter, 1.5m high furnace tube, 0.3568g of purified SWC nanotubes could be produced in 3 hours, with a Raman G / D ratio of 102.8. Figure 6 , 7 As shown.

[0097] Comparative Example 1

[0098] The steps are exactly the same as in Example 1, except that... Figure 1 In the single-walled carbon nanotube (SUV) preparation apparatus shown, the temperatures in the first and third temperature zones were 1300℃, and the second temperature zone was also 1300℃. The collection tank temperature was 500℃. Weighing and Raman spectroscopy revealed that within the reaction zone of a 60mm diameter, 1.5m high furnace tube, 0.9568g of product could be produced in 3 hours. Although the yield was high, Raman spectroscopy showed that the product was not pure SUV, with a G / D ratio of only 92. This is because during the growth or deposition of SUVs, the prolonged high-temperature isothermal zone caused some of the generated SUVs to convert into carbon black, resulting in a G / D ratio of only 92. Figure 8-10 As shown.

[0099] Comparative Example 2

[0100] The steps are exactly the same as in Example 1, except that... Figure 1 In the single-walled carbon nanotube (SWC) preparation apparatus shown, the first and third temperature zones were maintained at 500°C for SWC preparation. The collection tank temperature was also 500°C. Weighing and Raman spectroscopy revealed that within the reaction zone of a 60mm diameter, 1.5m high furnace tube, 0.2001g of net SWC product could be produced in 3 hours. However, Raman spectroscopy showed that the product contained only a very small amount of SWC nanotubes, with the majority being other carbon materials, resulting in a G / D ratio of only 12. This is because the reaction temperature did not reach the optimal temperature for SWC nanotube growth or deposition, failing to meet the growth conditions and leading to uneven SWC nanotube diameter and the presence of numerous impurities (amorphous carbon), resulting in a G / D ratio of only 12. Figure 11-13As shown. Comparative Example 2 and Comparative Example 2(2) represent images of single-walled carbon nanotubes at the 200 nm and 1 μm scales, respectively. Figure 10 , Figure 11 show.

[0101] Comparative Example 1 has a worse G / D ratio than Example 1 because the excessively long high-temperature isothermal zone during the growth or deposition of single-walled carbon nanotubes caused some of the generated single-walled carbon nanotubes to convert into carbon black, resulting in a G / D ratio of only 92. Comparative Example 2 has an even worse G / D ratio than Example 1 because the excessively long high-temperature isothermal zone during the growth or deposition of single-walled carbon nanotubes also caused some of the generated single-walled carbon nanotubes to convert into carbon black, resulting in a G / D ratio of only 12. The reaction temperatures in the first and third temperature zones of Comparative Example 2 did not reach the temperatures required for the growth or deposition of single-walled carbon nanotubes, thus failing to meet the growth conditions and preventing normal growth, resulting in a G / D ratio of only 12.

[0102] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing high-quality single-walled carbon nanotubes, characterized in that, Includes the following steps: 1) Prepare a mixture of liquid carbon source, iron source, co-catalyst and a small amount of water, and make it into a dispersion; 2) The dispersion is introduced from the top of the high-temperature furnace at a certain injection speed, while reducing gas and protective gas are introduced at the same time. The crude product of single-walled carbon nanotubes is synthesized by floating catalysis. The crude product is deposited in the lower part of the high-temperature furnace and in the collection tank. 3) Take out the crude product and calcine it in air at 450-500℃ for 1-1.5 hours to remove the amorphous carbon on the surface; 4) Purify the crude product treated in step 3) by stirring with strong acid at 20-25℃ to remove metal impurities; 5) Repeat steps 3) and 4) to remove metallic impurities from the crude product; The furnace tube of the high-temperature furnace is provided with a first temperature zone, a second temperature zone and a third temperature zone from the injection end to the collection tank end. The temperature of the second temperature zone is 1000-1300℃, the temperature of the first temperature zone and the third temperature zone are both 500-600℃, and the temperature of the collection tank is 500-600℃.

2. The method for preparing high-quality single-walled carbon nanotubes according to claim 1, characterized in that, The liquid carbon source is one or more of toluene, benzyl alcohol, or phenol; the iron source is one or more of ferric citrate, ferric nitrate, or ferric acetate; the co-catalyst is a sulfur source, which is one or more of thiophenol, selenophenol, or diethyl sulfide; the reducing gas is hydrogen sulfide, hydrogen, carbon monoxide, or methane; and the protective gas is an inert gas.

3. The method for preparing high-quality single-walled carbon nanotubes according to claim 1, characterized in that, The ratio of the iron source, liquid carbon source and co-catalyst is 1 g: 40~60 mL: 8 mL; the ratio of the reducing gas to the protective gas is 800-2000: 640-1600.

4. The method for preparing high-quality single-walled carbon nanotubes according to claim 1, characterized in that, The injection rate is 160-190 μL / min.

5. The method for preparing high-quality single-walled carbon nanotubes according to claim 1, characterized in that, The strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and aqua regia, and the stirring time of the purification process is 3-5 h.

6. The method for preparing high-quality single-walled carbon nanotubes according to claim 1, characterized in that, The ratio of furnace tube lengths in the first, second, and third temperature zones of the high-temperature furnace is 1:3:

1.

7. The method for preparing high-quality single-walled carbon nanotubes according to claim 6, characterized in that, The furnace tube is 1-3m long and has an inner diameter of 60-100mm.

Images