A continuous and stable production apparatus and method of single-walled carbon nanotubes

Abstract

The application discloses a continuous and stable preparation device and method of single-wall carbon nanotubes, relates to the technical field of nanometer carbon material preparation, and discloses a continuous and stable preparation device of single-wall carbon nanotubes.The structure of the device comprises hollow graphite, a graphite crucible, a plasma arc furnace body, an air inlet and a discharge port, wherein the hollow graphite serves as a cathode of the plasma arc furnace, and the graphite crucible serves as an anode of the plasma arc furnace.The plasma arc is caused between graphite electrodes, the disadvantages of the graphite cathode and the liquid catalyst anode in the conventional method are avoided, the evaporation rate of the catalyst is reduced, the problem of arc breaking caused by the sputtering of metal droplets in the liquid electrode and coking is overcome, a series of disadvantages of the conventional scheme are avoided through the convex crucible anode, the continuous stability of the reaction is greatly improved, and the stable and continuous preparation of the single-wall carbon nanotubes is realized.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically providing a continuous and stable preparation apparatus and method for single-walled carbon nanotubes. Background Technology

[0002] Single-walled carbon nanotubes (SUVs) are one-dimensional tubular nanomaterials formed by rolling up a single layer of graphene sheets. Their diameter typically ranges from 0.4 to 2 nanometers, while their length can reach several micrometers or even longer. Their structure can be viewed as a cylinder formed by a seamlessly connected honeycomb network of hexagonal carbon rings. Depending on the rolling method (chirality), SUVs can exhibit metallic or semiconducting properties. This unique structure endows SUVs with excellent physicochemical properties, showing broad application prospects in multiple fields. In the field of electronic devices, their high conductivity and semiconducting properties make them ideal materials for field-effect transistors, sensors, and flexible electrodes. In the energy field, SUVs are used as electrode materials in lithium-ion batteries, supercapacitors, and solar cells to improve energy density and charge / discharge efficiency. In the field of composite materials, their high strength and lightweight properties can be used to reinforce polymer, metal, or ceramic matrices, improving the mechanical properties and functionality of the materials. Furthermore, SUVs also have important applications in the biomedical field, such as as drug carriers, biosensors, and photothermal conversion agents in tumor therapy.

[0003] The main methods for preparing single-walled carbon nanotubes (SUVs) include arc discharge, laser evaporation, and chemical vapor deposition (CVD). Arc discharge generates high temperatures through discharge in an inert gas, causing graphite electrodes to evaporate and form SUVs. Laser evaporation uses a high-energy laser beam to bombard a graphite target containing a metal catalyst to generate SUVs. These two methods are typically used in laboratory research, but yields are low. Chemical vapor deposition is currently the most commonly used large-scale preparation method, which involves decomposing carbon-containing gases (such as methane or ethylene) at high temperatures and growing SUVs on the surface of a catalyst (such as iron, cobalt, or nickel). CVD offers advantages such as low cost, high controllability, and suitability for large-scale production, making it an important method for the industrial preparation of SUVs. Although challenges remain in the preparation of SUVs, including purity, chirality control, and dispersibility, their unique properties and broad application prospects make them a hot topic in nanomaterials research. However, balancing efficiency and quality remains a key challenge for the large-scale preparation and application of SUVs, and developing novel, efficient preparation equipment and methods remains a focus of current research.

[0004] Chinese invention patent CN 201910533219.0 discloses a method for preparing single-walled carbon nanotubes. The method involves using plasma arc evaporation of a catalyst metal to prepare the catalyst, while simultaneously introducing a carbon source gas. The high-temperature plasma simultaneously achieves high-temperature evaporation of the catalyst metal and cracking of the organic carbon source, directly preparing single-walled carbon nanotubes.

[0005] Chinese invention patent CN202111322714.0 attempts to partially solve the current problem by isolating the catalyst evaporation chamber and the growth chamber. However, the simple separation approach will cause the catalyst to aggregate and grow during transport and become ineffective. It will also reduce the thermal energy utilization rate, resulting in a decrease in yield and an increase in preparation cost.

[0006] Chinese invention patent 202210608795.9 utilizes the high-temperature zone formed by the electric arc confined in a deep graphite crucible to obtain a higher reaction temperature and a longer reaction residence time. At the same time, by utilizing the activation effect of electric arc plasma, single-walled carbon nanotubes with high crystallinity can be prepared. Summary of the Invention

[0007] The biggest drawback of these methods is the excessive evaporation of the catalyst, as well as the catalyst condensation and carbon nanotube coking issues that occur between the electrodes. These problems can lead to short circuits between the cathode and anode, causing arc interruption and a sharp decline in arc stability, making stable and continuous preparation difficult. Therefore, overcoming the arc interruption problem caused by short circuits is a crucial challenge that must be overcome to ensure the stability of product quality.

[0008] To address the above-mentioned problems, the present invention provides the following technical solution:

[0009] In one aspect, this invention provides a continuous and stable preparation apparatus for single-walled carbon nanotubes. The apparatus comprises hollow graphite, a graphite crucible, a plasma arc furnace body, an inlet, and a outlet. The hollow graphite serves as the cathode of the plasma arc furnace, and the graphite crucible serves as the anode.

[0010] The graphite crucible is a structure with a protruding middle section, used to hold the metal catalyst;

[0011] The graphite crucible is disposed at the bottom of the device, and the hollow graphite is disposed directly above the graphite crucible.

[0012] The diameter of the protruding part in the middle of the graphite crucible is approximately the same as the diameter of the hollow graphite.

[0013] Furthermore, the protruding part in the middle of the graphite crucible (1) is 2 to 20 centimeters higher than the liquid surface of the metal catalyst contained therein;

[0014] The plasma arc furnace has a power output of 20–1000 kW, a current of 100–10000 A, and a voltage of 10–500 V.

[0015] In another aspect, the present invention provides a method for the stable and continuous preparation of single-walled carbon nanotubes, characterized in that the method involves igniting an arc between the protruding parts of hollow graphite (4) and graphite crucible (1), heating and melting the first catalyst placed in the graphite crucible (1) through a plasma arc, and raising the furnace temperature of the furnace body (3) to a specified temperature; at this time, carbon source mixed gas and the second catalyst component are introduced into the furnace body (3), and a single-walled carbon nanotube product is obtained through a high-temperature chemical reaction, and then discharged from the furnace body (3) through the discharge port (5) to collect the single-walled carbon nanotube product.

[0016] Furthermore, the method specifically includes the following steps:

[0017] S1) The first catalyst is placed in a graphite crucible (1);

[0018] S2) Introduce plasma gas, turn on the plasma power supply, generate a plasma arc between the anode and cathode, melt the first catalyst in the graphite crucible (1) until the furnace temperature rises to the specified temperature.

[0019] S3) After mixing the carbon source gas and the carrier gas, the second catalyst is carried into the furnace body (3) through the hollow graphite cathode (4). The product is purged out of the furnace body (3) through the inlet (2) by inert gas. Single-walled carbon nanotube products are continuously collected.

[0020] Furthermore, in step S1), the first catalyst is iron, cobalt, nickel metal or a mixture thereof.

[0021] Furthermore, in step S1), the first catalyst is an alloy or mixture of iron, cobalt, nickel and a refractory metal, wherein the refractory metal element is molybdenum, tungsten, tantalum, niobium, hafnium or zirconium, and the weight ratio of the refractory metal element is 20-60%.

[0022] Furthermore, in step S2), the arc gas is any one, two or more of argon, nitrogen, helium, hydrogen, and water vapor, with a flow rate of 10 L / min to 500 L / min.

[0023] The specified temperature of the furnace is 900–1500℃.

[0024] Furthermore, in step S3), the carbon source gas is any one of methane, ethylene, acetylene, propylene, or propane;

[0025] The carrier gas is a mixture of nitrogen, argon, or helium with hydrogen, wherein the volume of carbon source gas is 10-80%, the volume of hydrogen is 0-35%, and the remainder is inert gas, with a flow rate of 10 L / min to 200 L / min.

[0026] Furthermore, in step S3), the second catalyst is a mixture of 50-95% metal powder and 5-50% co-catalyst powder;

[0027] The metal powder is any one or a combination of iron, cobalt, and nickel, with a particle size of 50 to 350 mesh;

[0028] The catalyst is any one of sulfur powder, selenium powder, iron sulfide, ferrous sulfide, nickel sulfide, cobalt sulfide, or a mixture thereof, with a particle size of 100-500 mesh;

[0029] The second catalyst feed rate is 0.1 g / min to 100 g / min.

[0030] Furthermore, the inert gas blown in step S3) is nitrogen, argon, or helium, with a flow rate of 0.5 L / min to 20 L / min.

[0031] Compared with existing technologies, the continuous and stable preparation apparatus and method for single-walled carbon nanotubes of the present invention have the following outstanding advantages:

[0032] This invention utilizes plasma arc initiation between graphite electrodes, which fully leverages the high-temperature plasma evaporation of the catalyst while avoiding the drawbacks of conventional methods involving graphite cathodes and liquid catalyst anodes for arc initiation. It reduces the catalyst evaporation rate and overcomes the problem of arc interruption caused by metal droplet sputtering and coking in the liquid electrode. By using a convex crucible anode, it avoids a series of drawbacks of conventional schemes, greatly improving the continuous stability of the reaction and achieving stable and continuous preparation of single-walled carbon nanotubes. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation device of the present invention;

[0034] Figure 2 Scanning electron microscope image of carbon nanotube products;

[0035] Figure 3 This is the Raman spectrum of the carbon nanotube product. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0037] like Figure 1 As shown, a continuous and stable preparation device for single-walled carbon nanotubes is disclosed. The device includes a hollow graphite core 4, a graphite crucible 1, a plasma arc furnace body 3, an air inlet 2, and a material outlet 5. The hollow graphite core 4 serves as the cathode of the plasma arc furnace, and the graphite crucible 1 serves as the anode.

[0038] The graphite crucible 1 is a structure with a protruding middle section, used to hold the metal catalyst;

[0039] The graphite crucible 1 is disposed at the bottom of the device, and the hollow graphite 4 is disposed directly above the graphite crucible 1.

[0040] The diameter of the protruding part in the middle of the graphite crucible 1 is approximately the same as the diameter of the hollow graphite 4.

[0041] The protruding part in the middle of the graphite crucible 1 is 2 to 20 centimeters higher than the liquid surface of the metal catalyst contained therein;

[0042] The plasma arc furnace has a power output of 20–1000 kW, a current of 100–10000 A, and a voltage of 10–500 V.

[0043] Example 1

[0044] use Figure 1 The apparatus shown is for the stable and continuous preparation of single-walled carbon nanotubes. The apparatus consists of a hollow graphite cathode 4, a graphite crucible anode 1, a furnace body 3, and an auxiliary system. The anode of the graphite crucible 1 protrudes in the middle and is 8 cm higher than the metal catalyst. Its diameter is similar to that of the cathode. The plasma power supply has a power of 150 kW, a current of 1000 A, and a voltage of 150 V.

[0045] Preparation process of single-walled carbon nanotubes:

[0046] S1) The first catalyst, Fe 60%-Mo 40% alloy, is placed in graphite crucible 1;

[0047] S2) Introduce argon plasma gas at a flow rate of 40 L / min, turn on the plasma power supply, and generate a plasma arc between the anode and cathode to melt the first catalyst in the graphite crucible 1 until the furnace temperature rises to 1300℃.

[0048] S3) After mixing the carbon source gas and the carrier gas, the mixture carries the second catalyst into the reactor through the hollow graphite cathode 4. The mixed gas contains 40% methane, 20% hydrogen, and the remainder argon, with a flow rate of 80 L / min. The second catalyst contains 10% sulfur powder and 90% iron powder with a particle size of 200 mesh, and the feed rate is 5 g / min. The product is purged out of the furnace through the inlet by inert gas, and the single-walled carbon nanotube product is continuously collected. The inert gas is argon, with a flow rate of 5 L / min.

[0049] The reaction proceeded steadily and continuously. After 72 hours, the product was collected and weighed, and the yield of single-walled carbon nanotubes was calculated to be approximately 890 g / h. The product was calcined in a muffle furnace at 900°C for 2 hours, and the ash content was weighed, yielding a calculated purity of 82.4%. The morphology of the product was observed using a scanning electron microscope as follows: Figure 2 As shown, the crystallinity is evaluated using the ratio of the peak intensities of the G and D peaks in the Raman spectrum. Figure 3As shown, the G / D ratio is ~64.5.

[0050] Example 2

[0051] use Figure 1 The apparatus shown is for the stable and continuous preparation of single-walled carbon nanotubes. The apparatus consists of a hollow graphite cathode 4, a graphite crucible anode 1, a furnace body, and an auxiliary system. The anode of the graphite crucible 1 protrudes in the middle and is 2 cm higher than the metal catalyst. Its diameter is similar to that of the cathode. The plasma power supply has a power of 20 kW, a current of 100 A, and a voltage of 20 V.

[0052] Preparation process of single-walled carbon nanotubes:

[0053] S1) The first catalyst, Fe 60%-Ta 40% alloy, is placed in graphite crucible 1;

[0054] S2) Introduce argon plasma gas at a flow rate of 10 L / min, turn on the plasma power supply, and generate a plasma arc between the anode and cathode to melt the first catalyst in the graphite crucible 1 until the furnace temperature rises to 900°C.

[0055] S3) After mixing the carbon source gas and the carrier gas, the mixture carries the second catalyst into the reactor through the hollow graphite cathode 4. The mixed gas contains 10% ethylene, 35% hydrogen, and the remainder argon, with a flow rate of 10 L / min. The second catalyst contains 10% selenium powder and 90% cobalt powder with a particle size of 200 mesh, and the feed rate is 0.1 g / min. The product is purged out of the furnace through the inlet by inert gas, and the single-walled carbon nanotube product is continuously collected. The inert gas is argon, with a flow rate of 0.5 L / min.

[0056] The reaction can proceed stably and continuously. After 72 hours of reaction, the product is collected and weighed to calculate the yield of single-walled carbon nanotubes, which can reach ~20 g / h. The ash content is weighed after calcination at 900℃ in a muffle furnace for 2 hours, and the purity of the product is calculated to be 76.3%.

[0057] Example 3

[0058] use Figure 1 The adoption shown is as follows Figure 1 The apparatus shown is for the stable and continuous preparation of single-walled carbon nanotubes. The apparatus consists of a hollow graphite cathode 4, a graphite crucible anode 1, a furnace body, and an auxiliary system. The anode of the graphite crucible 1 protrudes in the middle and is 20 cm higher than the metal catalyst. Its diameter is similar to that of the cathode. The plasma power supply has a power of 1000 kW, a current of 10000 A, and a voltage of 100 V.

[0059] Preparation process of single-walled carbon nanotubes:

[0060] S1) Place the first catalyst iron in graphite crucible 1;

[0061] S2) Introduce argon plasma gas at a flow rate of 500 L / min, turn on the plasma power supply, and generate a plasma arc between the anode and cathode to melt the first catalyst in the graphite crucible 1 until the furnace temperature rises to 1500℃.

[0062] S3) After mixing the carbon source gas and the carrier gas, the mixture carries the second catalyst into the reactor through the hollow graphite cathode 4. The mixed gas contains 80% acetylene, 15% hydrogen, and the remainder argon, with a flow rate of 200 L / min. The second catalyst consists of 20% ferrous sulfide powder and 80% nickel powder with a particle size of 200 mesh and a feed rate of 100 g / min. The product is purged out of the furnace through the inlet by inert gas, and single-walled carbon nanotube products are continuously collected. The inert gas argon has a flow rate of 20 L / min.

[0063] The reaction can proceed stably and continuously. After 72 hours, the product is collected and weighed to calculate the yield of single-walled carbon nanotubes, which can reach ~3570 g / h. The ash content is weighed after calcination at 900℃ for 2 hours in a muffle furnace, and the purity of the product is calculated to be 75.6%.

[0064] Example 4

[0065] use Figure 1 The apparatus shown is for the stable and continuous preparation of single-walled carbon nanotubes. The apparatus consists of a hollow graphite cathode 4, a graphite crucible anode 1, a furnace body, and an auxiliary system. The anode of the graphite crucible 1 protrudes in the middle and is 8 cm higher than the metal catalyst. Its diameter is similar to that of the cathode. The plasma power supply has a power of 300 kW, a current of 1500 A, and a voltage of 200 V.

[0066] Preparation process of single-walled carbon nanotubes:

[0067] S1) The first catalyst, Fe60%-Co40% alloy, is placed in graphite crucible 1;

[0068] S2) Introduce argon plasma gas at a flow rate of 20 L / min, turn on the plasma power supply, and generate a plasma arc between the anode and cathode to melt the first catalyst in the graphite crucible 1 until the furnace temperature rises to 1000℃.

[0069] S3) After mixing the carbon source gas and the carrier gas, the mixture carries the second catalyst into the reactor through the hollow graphite 4 cathode. The mixed gas contains 40% propylene, 20% hydrogen, and the remainder argon, with a flow rate of 100 L / min. The second catalyst consists of 40% Ni3S4 powder and 60% iron powder with a particle size of 200 mesh and a feed rate of 7.5 g / min. The product is purged out of the furnace through the inlet by inert gas, and single-walled carbon nanotubes are continuously collected. The inert gas argon has a flow rate of 10 L / min.

[0070] The reaction can proceed stably and continuously. After 72 hours, the product is collected and weighed to calculate the yield of single-walled carbon nanotubes, which can reach ~1450 g / h. The ash content is weighed after calcination at 900℃ for 2 hours in a muffle furnace, and the purity of the product is calculated to be 83.4%.

[0071] Example 5

[0072] Adopting such Figure 1 The apparatus shown is for the stable and continuous preparation of single-walled carbon nanotubes. The apparatus consists of a hollow graphite cathode 4, a graphite crucible anode 1, a furnace body, and an auxiliary system. The anode of the graphite crucible 1 protrudes in the middle, 5 cm above the metal catalyst, and its diameter is comparable to that of the cathode. The plasma power supply has a power of 300 kW, a current of 1500 A, and a voltage of 200 V.

[0073] Preparation process of single-walled carbon nanotubes:

[0074] S1) The first catalyst, Fe30%-Co30%-Ta40% alloy, is placed in graphite crucible 1;

[0075] S2) Introduce argon plasma gas at a flow rate of 20 L / min, turn on the plasma power supply, and generate a plasma arc between the anode and cathode to melt the first catalyst in the graphite crucible 1 until the furnace temperature rises to 1100℃.

[0076] S3) After mixing the carbon source gas and the carrier gas, the mixture carries the second catalyst into the reactor through the hollow graphite cathode 4. The mixed gas contains 40% propane, 20% hydrogen, and the remainder argon, with a flow rate of 100 L / min. The second catalyst contains 20% CoS powder and 80% iron powder with a particle size of 200 mesh, and the feed rate is 7.5 g / min. The product is purged out of the furnace through the inlet with inert gas, and the single-walled carbon nanotube product is continuously collected. The inert gas is argon, with a flow rate of 10 L / min.

[0077] The reaction can proceed stably and continuously. After 72 hours of reaction, the product was collected and weighed to calculate the yield of single-walled carbon nanotubes, which can reach ~1785 g / h. The ash content was weighed after calcination at 900℃ in a muffle furnace for 2 hours, and the purity of the product was calculated to be 84.5%.

[0078] Comparative Example 1

[0079] The comparative example had the same equipment and experimental parameters as Example 1, except that the graphite crucible 1 in the comparative example did not have a central protruding structure at the anode; otherwise, they were identical. Due to arc interruption caused by blockage after the reaction, the reaction was discontinuous, and the experiment could only be conducted for 2 hours. The product yield was calculated to be ~245 g / h, and thermal analysis showed a product purity of 43.5%.

[0080] The comparative experimental results of the examples are summarized below:

[0081]

[0082] As can be seen from the above data summary, the growth efficiency of single-walled carbon nanotubes in the embodiments of the present invention is significantly improved, and the purity and growth efficiency of single-walled carbon nanotubes are significantly enhanced.

[0083] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the continuous and stable preparation of single-walled carbon nanotubes, characterized in that, The apparatus for implementing the method includes a hollow graphite (4), a graphite crucible (1), a plasma arc furnace body (3), an air inlet (2), and a material outlet (5), wherein the hollow graphite (4) serves as the cathode of the plasma arc furnace, and the graphite crucible (1) serves as the anode of the plasma arc furnace. The graphite crucible (1) is a structure with a protruding middle section, used to hold the metal catalyst; The graphite crucible (1) is located at the bottom of the device, and the hollow graphite (4) is located directly above the graphite crucible (1). The diameter of the protruding part in the middle of the graphite crucible (1) is equivalent to the diameter of the hollow graphite (4); The method involves igniting an arc between the protruding parts of the hollow graphite (4) and the graphite crucible (1), heating and melting the first catalyst placed in the graphite crucible (1) through a plasma arc, and raising the furnace temperature of the furnace body (3) to a specified temperature; at this time, the carbon source mixture and the second catalyst component are introduced into the furnace body (3), and a single-walled carbon nanotube product is obtained through a high-temperature chemical reaction, and then discharged from the furnace body (3) through the discharge port (5) to collect the single-walled carbon nanotube product; The protruding part in the middle of the graphite crucible (1) is 2-20 cm higher than the liquid surface of the metal catalyst contained therein; The plasma arc furnace has a power output of 20~1000 kW, a current of 100~10000 A, and a voltage of 10~500 V.

2. The continuous and stable preparation method of single-walled carbon nanotubes according to claim 1, characterized in that, The method specifically includes the following steps: S1) Place the first catalyst in a graphite crucible (1); S2) Introduce plasma gas, turn on the plasma power supply, generate a plasma arc between the anode and cathode, melt the first catalyst in the graphite crucible (1) until the furnace temperature rises to the specified temperature. S3) After mixing the carbon source gas and the carrier gas, the second catalyst is carried into the furnace body (3) through the hollow graphite (4) cathode. The product is purged out of the furnace body (3) by inert gas through the gas inlet (2) and the single-walled carbon nanotube product is continuously collected.

3. The method for continuous and stable preparation of single-walled carbon nanotubes according to claim 2, characterized in that, The first catalyst in step S1) is iron, cobalt, nickel metal or a mixture thereof.

4. The continuous and stable preparation method of single-walled carbon nanotubes according to claim 2, characterized in that, In step S1), the first catalyst is an alloy or mixture of iron, cobalt, nickel and a refractory metal, wherein the refractory metal element is molybdenum, tungsten, tantalum, niobium, hafnium or zirconium, and the weight ratio of the refractory metal element is 20-60%.

5. The method for continuous and stable preparation of single-walled carbon nanotubes according to claim 2, characterized in that, In step S2), the arc gas is any one, two or more of argon, nitrogen, helium, hydrogen, and water vapor, with a flow rate of 10 L / min to 500 L / min. The specified temperature of the furnace is 900~1500℃.

6. The method for continuous and stable preparation of single-walled carbon nanotubes according to claim 2, characterized in that, In step S3), the carbon source gas is any one of methane, ethylene, acetylene, propylene, or propane. The carrier gas is a mixture of nitrogen, argon, or helium with hydrogen, wherein the volume of carbon source gas is 10-80%, the volume of hydrogen is 0-35%, and the remainder is inert gas, with a flow rate of 10 L / min to 200 L / min.

7. The method for continuous and stable preparation of single-walled carbon nanotubes according to claim 2, characterized in that, In step S3), the second catalyst is a mixture of 50-95% metal powder and 5-50% co-catalyst. The metal powder is any one or a combination of iron, cobalt, and nickel, with a particle size of 50-350 mesh; The catalyst is any one of sulfur powder, selenium powder, iron sulfide, ferrous sulfide, nickel sulfide, cobalt sulfide, or a mixture thereof, with a particle size of 100-500 mesh; The second catalyst feed rate is 0.1 g / min to 100 g / min.

8. The method for continuous and stable preparation of single-walled carbon nanotubes according to claim 2, characterized in that, The inert gas blown in step S3) is nitrogen, argon or helium, with a flow rate of 0.5 L / min to 20 L / min.

Images