Method for continuously preparing single-walled carbon nanotubes

Abstract

The invention relates to a method for continuously preparing a single-walled carbon nanotube, which comprises the following steps of: uniformly mixing organic metal and a growth promoter in proportion to form a catalyst, adding the catalyst into a dust spraying device, connecting each gas pipeline and a preheating furnace inlet, connecting an outlet of the preheating furnace with a vertical tube furnace, and sealing the whole device; firstly introducing inert gas to remove air, then preheating the furnace, and heating the vertical tube furnace; after the temperature is stable, the injection device injects a catalyst into the preheating furnace, the preheating furnace and the vertical tube furnace are kept at the constant temperature, and the single-walled carbon nanotubes continuously grow; after the catalyst is consumed, stopping gas supply, turning off a power supply, and taking a sample at room temperature. The catalyst is fully preheated before entering a vertical tube furnace, and the reaction activity of the catalyst reaches the highest; the temperature in the furnace chamber of the reactor is constant, organic gas is fully contacted with a catalyst, carrier gas and reducing gas and is uniformly heated, and continuous growth of the carbon nanotubes is facilitated; the energy consumption is low, the occupied area is small, the operation is simple, continuous production can be realized, the productivity is high, the length-diameter ratio is large, the G / D value is large, and the specific surface area is large.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon nanotube materials, and in particular relates to a method for continuously preparing single-walled carbon nanotubes. Technical Background

[0002] In order to significantly increase the energy density of batteries, improve fast charging capabilities and reduce costs, the current technical solution is to add single-walled carbon nanotube conductive slurry to the battery to meet the needs. Single-walled carbon nanotube conductive slurry has unparalleled conductivity, high strength, high flexibility, high aspect ratio and other characteristics, as well as the ability to form a developed conductive network inside the material when added in low doses. At the same time, single-walled carbon nanotubes can cover the surface of silicon particles after being introduced into the silicon negative electrode and establish highly conductive and lasting connections between silicon particles. The connections established between silicon particles are very tight, long-lasting, conductive and strong. Even when the volume of silicon negative electrode particles expands and cracks begin to appear, these particles can still be well connected through single-walled carbon nanotubes, thereby preventing the negative electrode material from breaking, so that the silicon negative electrode has a perfect cycle life; in addition, single-walled carbon nanotubes have application potential in many fields such as aerospace, integrated circuits, conductive plastics, energy storage devices, structural and functional composite materials. Therefore, the demand for single-walled carbon nanotubes will increase in the future, and a continuous, simple and efficient method is crucial.

[0003] The application publication number is CN 110790259 A, which discloses a method for preparing single-walled carbon nanotubes in batches, wherein the first step is to add a metal organic compound to an organic solvent, emulsify the compound, and prepare a catalyst precursor solution; the second step is to continuously pass the catalyst precursor solution, reducing gas, inert gas, and carbon source gas obtained in the first step into a reaction device kept at 600°C-1500°C, and continuously react to obtain single-walled carbon nanotubes. However, the temperature, emulsification time, and stirring time in the emulsification process of the first step of this method are difficult to effectively control, and the carbon content of the obtained single-walled carbon nanotubes is about 85%, which does not meet the current demand for carbon content in the conductive slurry of lithium batteries, and further acidification purification or high-temperature purification is required.

[0004] The application publication number is CN 116692835 A, which discloses a device and method for preparing single-walled carbon nanotubes on a large scale. The method is to divide the synthesis furnace body into two sections with different diameters and lengths, and preheat the carrier gas (preheating temperature is 500~900℃) and the carbon source and promoter (preheating temperature is 100~400℃) respectively, and finally achieve batch preparation of single-walled carbon nanotubes under the condition of synthesis temperature as high as 1400~1800℃. However, the carrier gas of this method is pure hydrogen and the instantaneous flow rate is very large, which has a very high risk factor. In addition, the tube length of the grown single-walled carbon nanotubes is obviously different, and the tube diameter distribution is uneven, so the performance is somewhat different from that of pure single-walled carbon nanotubes; on the other hand, it is not suitable for batch production from the perspective of energy consumption. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that the existing method for preparing single-walled carbon nanotubes is not easy to prepare continuously, and to provide a method for preparing single-walled carbon nanotubes continuously.

[0006] To achieve the above purpose, the present invention adopts the following technical solution.

[0007] The method for continuously preparing single-walled carbon nanotubes described in the present invention is characterized in that organic metal (catalyst precursor), growth promoter sulfur powder or sulfur-containing compound (such as iron sulfide, etc.), organic gas (carbon source), reducing gas (carrier), inert gas (protective gas) are heated simultaneously in a preheating furnace, and single-walled carbon nanotubes are grown by a floating catalyst chemical vapor deposition method in a vertical tube furnace. Specifically, the method includes the following steps.

[0008] (1) Put the organic metal and the growth promoter in a molar ratio of 40-20:1 into a stirring tank and mix them thoroughly to form a catalyst for use. The preferred molar ratio of the organic metal and the growth promoter is 30:1.

[0009] (2) Add the evenly mixed catalyst into the precision dust injection device, and connect the device to the preheating furnace through a pipeline.

[0010] (3) Connect the pipes of organic gas, reducing gas and inert gas connected with mass flow meters to the inlet of the preheating furnace respectively, and connect the outlet of the preheating furnace to the feed port of the vertical tube furnace through a pipe. Then seal the entire device. After confirming that the airtightness is good at the tail gas end, first pass an inert gas with a flow rate of 1000sccm for 20 minutes to remove the residual air in the entire device. Then, heat the preheating furnace and the vertical tube furnace separately in an inert gas atmosphere. The preheating furnace is heated to 100℃-300℃, and the vertical tube furnace is heated to 1100℃-1300℃. When the temperature stabilizes, turn on the precision dust injection device, adjust the gas speed so that the catalyst enters the preheating furnace at 20g / h, and adjust the pipeline at the same time so that the inert gas carries the organic gas and reducing gas into the preheating furnace and then into the vertical tube furnace. The entire pipeline is kept in a heated state at a temperature of 200±5°C. Finally, the preheating furnace and the vertical tube furnace are kept at a constant temperature to allow the single-walled carbon nanotubes to grow continuously. The growth of the single-walled carbon nanotubes is observed at the collecting end. When the catalyst in the precision dust injection device is consumed, immediately adjust the pipeline to stop the introduction of organic gas and reducing gas, and turn off the power of the preheating furnace and the tube furnace heater. After the sample in the receiving box is cooled to room temperature, take out the sample.

[0011] Furthermore, the organic metal in step (1) is one or a mixture of ferrocene, cobaltocene, nickelocene, manganocene, and chromocene; and the growth promoter is one or a mixture of sulfur powder, iron sulfide, and ferrous sulfide.

[0012] Furthermore, the preheating furnace and the vertical tube furnace described in step (2) both adopt an automatic programmed heating mode.

[0013] Furthermore, the organic gas in step (3) is one or a mixture of natural gas, ethane, ethylene, acetylene, propane, and propylene.

[0014] Furthermore, the reducing gas in step (3) is one or a mixture of hydrogen, ammonia and carbon monoxide.

[0015] Furthermore, the inert gas in step (3) is nitrogen, argon or helium.

[0016] Furthermore, the temperature of the preheating furnace in step (3) is preferably raised to 200°C, and the temperature of the tubular furnace is preferably raised to 1200°C.

[0017] Compared with the prior art, the present invention has the following technical effects.

[0018] (1) The preheating furnace used in the present invention allows the catalyst to be fully preheated before entering the vertical tube furnace, thereby achieving the strongest reaction activity after entering the vertical tube furnace.

[0019] (2) The vertical tubular furnace reactor used in the present invention can ensure a constant temperature in the furnace chamber, so that the organic gas is evenly heated after being fully in contact with the catalyst, carrier gas, and reducing gas, which is beneficial to the continuous growth of single-walled carbon nanotubes. In addition, the vertical furnace reactor has low energy consumption, small footprint, and simple operation process, which is convenient for engineering scale-up and mass production. As long as the evenly mixed catalyst is continuously added to the precision dust injection device, uninterrupted continuous production can be achieved.

[0020] (3) The carrier gas and reducing gas used in the present invention are cheap, readily available, and environmentally friendly.

[0021] (4) The single-walled carbon nanotubes prepared by the present invention have high production capacity, large aspect ratio, large G / D value, and large specific surface area, and have good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a scanning electron microscope image of the single-walled carbon nanotube prepared by the present invention.

[0023] Figure 2 It is a transmission electron microscope image of the single-walled carbon nanotube prepared by the present invention.

[0024] Figure 3 It is a Raman spectrum diagram of the single-walled carbon nanotube prepared by the present invention. DETAILED DESCRIPTION

[0025] The following specific embodiments describe the present invention in detail.

[0026] The methods described in the following examples are conventional methods unless otherwise specified; the materials and reagents described are commercially available unless otherwise specified. Example 1

[0027] The pipelines of natural gas, hydrogen and argon connected with mass flow meters are respectively connected to the inlet of the preheating furnace, and the outlet of the preheating furnace is connected to the feed port of the vertical tube furnace through a pipeline. Then the whole device is sealed. After confirming that the airtightness is good at the tail gas end, argon gas with a flow rate of 1000sccm is introduced for 20 minutes to remove the residual air in the whole device. Then, the preheating furnace and the vertical tube furnace are heated up in an argon atmosphere, the preheating furnace is heated to 200℃, and the vertical tube furnace is heated to 1200℃. When the temperature stabilizes, turn on the precision dust injection device, adjust the gas speed so that the catalyst enters the preheating furnace at 20g / h, and adjust the pipeline flowmeter so that the flow ratio of argon, natural gas, and hydrogen enters the preheating furnace and then enters the vertical tubular furnace according to 30:1:6. The entire pipeline system is kept in a heated state at 200°C. Finally, the preheating furnace and the vertical tubular furnace are kept at a constant temperature to allow continuous growth of single-walled carbon nanotubes. The growth of single-walled carbon nanotubes is observed in the collecting device. When the catalyst in the precision dust injection device is consumed, immediately turn off the natural gas and hydrogen flowmeters, reduce the flow of argon, and turn off the power of the preheating furnace and tubular furnace heaters. After the sample in the receiving box is cooled to room temperature, take out the sample.

[0028] The single-walled carbon nanotubes were tested by SEM, TEM and Raman spectroscopy. The diameter of the product was characterized by SEM and TEM, while the G / D ratio of the Raman spectrum was used to characterize the degree of defect of the product. The test results are shown in Figure 1 , Figure 2 , Figure 3 And as shown in Table 1.

[0029] Examples 2-7.

[0030] The specific steps provided in Example 1 are adopted, and the differences are shown in the following table. The characterization data of the generated single-walled carbon nanotubes are also shown in the following table.

[0031]

[0032] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for continuously preparing single-walled carbon nanotubes, characterized in that: The following steps are involved: (1) placing the organic metal and the growth promoter in a molar ratio of 40-20:1 into a stirring tank and mixing them thoroughly to form a catalyst for use; (2) Add the evenly mixed catalyst into the precision dust injection device, and connect the device to the preheating furnace through a pipeline; (3) Connect the pipelines of organic gas, reducing gas and inert gas connected with mass flow meters to the inlet of the preheating furnace respectively. The outlet of the preheating furnace is connected to the feed inlet of the vertical tube furnace through a pipeline, and then seal the entire device; (4) First, introduce an inert gas with a flow rate of 1000 sccm for 20 minutes to remove the residual air in the entire device, and then heat the preheating furnace and the vertical tube furnace respectively under the inert gas atmosphere, with the preheating furnace being heated to 100°C-300°C and the vertical tube furnace being heated to 1100°C-1300°C; (5) When the temperature is stable, turn on the precision dust injection device, adjust the gas speed so that the catalyst enters the preheating furnace at 20g / h, and adjust the pipeline so that the inert gas carries the organic gas and reducing gas into the preheating furnace and then into the vertical tube furnace. The entire pipeline is kept in a heated state at a temperature of 200±5℃. Finally, the preheating furnace and the vertical tube furnace are kept at a constant temperature to allow the single-walled carbon nanotubes to grow continuously. (6) Observe the growth of single-walled carbon nanotubes at the collection end. When the catalyst in the precision dust injection device is consumed, immediately adjust the pipeline to stop the introduction of organic gas and reducing gas, and turn off the power of the preheating furnace and tubular furnace heater. After the sample in the collection box cools to room temperature, take out the sample.

2. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The molar ratio of the organic metal to the growth promoter is 30:

1.

3. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The organic metal is one of ferrocene, cobaltocene, nickelocene, manganocene and chromocene, or a mixture of several of them; the growth promoter is one of sulfur powder, iron sulfide and ferrous sulfide, or a mixture of several of them.

4. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The preheating furnace and the vertical tube furnace both adopt an automatic programmed temperature rising mode.

5. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The organic gas is one of natural gas, ethane, ethylene, acetylene, propane and propylene, or a mixture of several of them.

6. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The reducing gas is one of hydrogen, ammonia and carbon monoxide or a mixture of several of them.

7. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The inert gas is nitrogen, argon or helium.

8. The method for continuously preparing single-walled carbon nanotubes according to claim 1, characterized in that: The preheating furnace described in step (4) is heated to 200°C, and the tubular furnace is heated to 1200°C.

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