Device and method for preparing single-walled carbon nanotube by two-step method

Abstract

The invention discloses a device and a method for preparing a single-walled carbon nanotube by a two-step method. The device comprises a carbon nanotube growth chamber, a product collection module, a catalyst supply module, a carbon source supply module and an etching agent supply module, the carbon source supply module is used for introducing a first airflow containing a carbon source in a first direction, the etching agent supply module is used for introducing a second airflow containing an etching agent in a second direction, and the first direction is opposite to the second direction so that the airflow intersects to form a vortex; the catalyst supply module introduces catalyst particles in a third direction, and the third direction points to the position near the vortex; and the product collecting module is arranged above the vortex and is used for collecting the formed single-walled carbon tubes. Controllable preparation of catalyst nanoparticles and ordered separation of carbon nanotube growth steps are realized, the influence of hybrid variables on the reaction is reduced, the vortex is formed by opposite intersection of airflow, and the problem of local deposition and blockage of tangential laminar flow is avoided by the vortex, so that the influence on the quality and continuous growth of the carbon nanotubes is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of carbon nanomaterials, and in particular to a device and method for preparing single-walled carbon nanotubes in two steps. Background Art

[0002] Single-walled carbon nanotubes are a type of one-dimensional carbon nanomaterial. Structurally, they can be roughly viewed as tubular nanomaterials formed by curling up a single layer of graphene. They have a huge aspect ratio and excellent electrical, mechanical, and thermal properties. Therefore, they can be widely used in a variety of application scenarios such as enhancing electrical properties, enhancing mechanical properties, and photothermal conversion. They are an indispensable type of cutting-edge material in the process of moving towards high-end manufacturing.

[0003] The main methods for preparing single-walled carbon nanotubes include floating catalyst CVD method (FCCVD method, Nanoscale, 2020, 12, 12263), laser ablation method (Science, 1996, 273: 483), high-pressure carbon monoxide method (The Journal of Physical Chemistry B, 2001, 105: 8297-8301), arc method (Nature, 1991, 354: 56), etc. Each technical route has its own advantages and disadvantages. Taking the FCCVD method as an example, although the purity and crystallinity of the prepared single-walled carbon nanotube products are very high, the hourly production capacity of a device still remains at the gram level, and large-scale mass production cannot be achieved. The current difficulties in the large-scale preparation technology of single-walled carbon nanotubes can be summarized as follows: (1) Efficient preparation of catalysts; (2) Efficient conversion of carbon sources; (3) Integration of reaction equipment.

[0004] Having both high crystallinity and high yield is a huge and comprehensive proposition, and the arc method is currently the only technical route that is expected to achieve mass production of single-walled carbon nanotubes. Its core essence is that the growth rate of the catalyst and the cracking rate of the carbon source have been greatly improved thanks to the ultra-high temperature provided by the arc, but disadvantages also come with it. The ultra-high temperature of the arc (greater than 10,000°C) makes it difficult to control the decomposition of the catalyst precursor and the carbon source precursor, so it is difficult to regulate the purity and crystallinity of the generated single-walled carbon nanotube products.

[0005] Therefore, how to achieve large-scale preparation of high-purity and high-crystallinity single-walled carbon nanotubes is a technical problem that needs to be solved urgently. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a device and method for preparing single-walled carbon nanotubes in two steps.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0008] In a first aspect, the present invention provides a two-step method for preparing single-walled carbon nanotubes, comprising: a carbon nanotube growth chamber, a product collection module, a catalyst supply module, a carbon source supply module, and an etchant supply module;

[0009] The product collection module, catalyst supply module, carbon source supply module and etchant supply module are fixedly mounted on the cavity wall of the carbon nanotube growth chamber and are in communication with the internal reaction chamber of the carbon nanotube growth chamber;

[0010] The carbon source supply module is used to pass a first gas flow containing a carbon source into the reaction chamber in a first direction, and the etchant supply module is used to pass a second gas flow containing an etchant into the reaction chamber in a second direction, and the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow converge to form a vortex; the catalyst supply module is used to pass catalyst particles into the reaction chamber in a third direction, and the third direction points to the vicinity of the position of the vortex; the product collection module is arranged above the vortex, and is used to collect single-walled carbon nanotubes formed in the vortex.

[0011] In a second aspect, the present invention also provides a two-step method for preparing single-walled carbon nanotubes, which comprises:

[0012] A first gas flow containing a carbon source is introduced into a reaction chamber in a first direction, a second gas flow containing an etchant is introduced into the reaction chamber in a second direction, and catalyst particles are introduced into the reaction chamber in a third direction, wherein the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow meet to form a vortex, and the third direction points to the vicinity of the location of the vortex;

[0013] The single-walled carbon nanotubes formed in the vortex and carried by the flow field of the vortex are collected above the vortex.

[0014] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention at least include:

[0015] The preparation device and method provided by the present invention avoid the mutual interference phenomenon that occurs among the three in the early stage of the reaction in the traditional preparation method by introducing the catalyst, carbon source and etchant into the reaction chamber through different channels, especially avoids the mutual interference between the carbon source and the catalyst, provides a controllable and stable catalyst particle formation process, realizes the orderly separation of the controllable preparation of catalyst nanoparticles and the carbon nanotube growth step, and reduces the influence of mixed variables on the reaction; in addition, the opposite intersection of the carbon source gas flow and the etchant gas flow is used to form a vortex, which avoids the problem of local siltation and blockage of the tangential laminar flow, thereby avoiding the influence on the quality and continuous growth of the carbon nanotubes, and finally realizes the large-scale preparation of single-walled carbon nanotubes with high purity and high crystallinity.

[0016] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a device for preparing single-walled carbon nanotubes by a two-step method provided in a typical embodiment of the present invention;

[0018] Figure 2 This is a scanning electron microscope photograph of a product obtained in a typical embodiment of the present invention;

[0019] Figure 3 This is a transmission electron microscope photo of a product obtained in a typical embodiment of the present invention;

[0020] Figure 4 This is a Raman spectrum test diagram of a product obtained in a typical implementation case of the present invention;

[0021] Figure 5 This is a thermogravimetric test diagram of a product obtained from a typical comparative case of the present invention;

[0022] Figure 6 This is a thermogravimetric test diagram of a product obtained from a typical comparative case of the present invention;

[0023] Figure 7 This is a Raman spectrum test diagram of a product obtained in a typical comparative case of the present invention;

[0024] Figure 8 This is a Raman spectrum test diagram of a product obtained in a typical comparative case of the present invention;

[0025] Fig. 9 This is a thermogravimetric test diagram of a product obtained from a typical comparative case of the present invention.

[0026] Explanation of the accompanying drawings: 1. Induction plasma unit; 2. Catalyst growth unit; 3. Carbon source supply module; 4. Etchant supply module; 5. Carbon nanotube growth chamber; 6. Material outlet channel; 7. Product collection module. DETAILED DESCRIPTION

[0027] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0029] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0030] An embodiment of the present invention provides a device for preparing single-walled carbon nanotubes by a two-step method, which includes: a carbon nanotube growth chamber, a product collection module, a catalyst supply module, a carbon source supply module and an etchant supply module; the product collection module, the catalyst supply module, the carbon source supply module and the etchant supply module are fixed on the cavity wall of the carbon nanotube growth chamber and are connected to the internal reaction chamber of the carbon nanotube growth chamber; the carbon source supply module is used to pass a first gas flow containing a carbon source into the reaction chamber in a first direction, and the etchant supply module is used to pass a second gas flow containing an etchant into the reaction chamber in a second direction, and the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow converge to form a vortex; the catalyst supply module is used to pass catalyst particles into the reaction chamber in a third direction, and the third direction points to the vicinity of the position of the vortex; the product collection module is arranged above the vortex, and is used to collect single-walled carbon nanotubes formed in the vortex.

[0031] The present invention adopts a two-step approach. The first step is to form catalyst particles using an induction plasma torch as a high-temperature source, for example, the catalyst precursor and the inhibitor are quickly evaporated and cracked under the high temperature of the plasma to form extremely fine nanoparticles; the second step is to introduce a carbon source and an etchant into another cavity to allow them to meet the catalyst particles, complete the growth of carbon nanotubes, and quickly discharge them with the vortex airflow.

[0032] The general existing technologies often adopt a one-step approach. For example, some existing technologies also propose a technical solution of using plasma to form catalyst particles to prepare single-walled carbon nanotubes. However, in these existing technologies, the formation of catalyst particles and the growth of carbon nanotubes are often completed in the same spatial area. The inventors found that this is not conducive to the control of microscopic variables and cannot achieve the purpose of large-scale preparation of high purity and high crystallinity.

[0033] In terms of the preparation principle of carbon nanotubes, the sequence is as follows: (1) First, catalyst particles of appropriate size are formed; (2) Then, the catalyst particles are contacted with the carbon source, and then the carbon nanotubes grow. It can be seen that no matter which method is used, its core should comply with the above principles, but the difficulty in preparing single-walled carbon nanotubes lies precisely in how to control the uniform preparation of catalyst particles and under what conditions they are contacted with the carbon source.

[0034] Therefore, from the perspective of controlling variables, the disadvantage of the one-step method is that there are too many variables in the same spatial region, making it difficult to achieve the preparation of high-quality single-walled carbon nanotubes; the advantage of the two-step method of the present invention is that the preparation of the catalyst and the growth of carbon nanotubes are separated, making it easier to regulate the variables and thereby achieve the preparation of high-quality carbon nanotubes; the difference in effect between different growth modes is mainly reflected in the regulation of nanocatalyst particles. It is worth noting that nanoscale catalyst particles are the core key to the preparation of high-quality single-walled carbon nanotubes.

[0035] Thanks to the two-step design, the present invention can control a series of parameters in the first step, giving priority to the controllable adjustment of the size distribution and components of the catalyst particles, which can be learned from the catalyst size distribution. The one-step method is to concentrate the catalyst preparation, carbon source cracking, and carbon nanotube growth in one chamber. The formation of catalyst particles, decomposition of carbon sources and other processes interfere with each other, and the distribution of catalyst particle size will be disordered. The variable parameters involved are far beyond the present invention, and it is very difficult to repeat and scale up when conducting pilot or mass production tests.

[0036] In addition, many of the preparation processes proposed in the prior art all introduce the etchant in one direction and in the same direction (i.e., the flow direction of the etchant is consistent with the flow direction of the carbon source or the two flow in the same direction), which is also significantly different from the present invention from a microscopic perspective, specifically in the following aspects: (1) the counter-flow of the carbon source gas flow and the etchant gas flow can reduce the pre-contact and pre-reaction between the etchant and the reactant, and avoid interfering with the decomposition process of the carbon source; (2) from the perspective of the step in which the etchant takes effect, it occurs after the carbon source and the catalyst contact and react. Therefore, from the perspective of controlling variables, introducing the etchant in a counter-flow and separate form is conducive to maintaining the activity of the catalyst particles; (3) the counter-flow contact is more likely to form vortices, which is very important for improving the quality of carbon nanotubes and the continuity of preparation. However, the existing unidirectional tangential gas flow will have a weak gas flow field area in the furnace body, which is not conducive to the formation of vortices, which will cause the carbon nanotubes to accumulate and block locally, ultimately affecting the quality of the carbon nanotubes and the continuous discharge. Therefore, the counter-flow design is also one of the core designs of the present invention.

[0037] As for some specific structural features related to the airflow field, in some embodiments, the carbon source supply module is arranged on one side of the carbon nanotube growth chamber, the etchant supply module is arranged on the other side opposite to the carbon nanotube growth chamber, and the first direction and the second direction are both arranged horizontally and both point to the center of the vortex.

[0038] In some embodiments, the carbon nanotube growth chamber is further provided with a heating unit for adjusting the temperature in the reaction chamber, and directly below the product collection module, the vortex forms a vertically upward flow field under the influence of heat.

[0039] In the above scheme, the horizontally opposed setting is relatively important for forming a stable and centered vortex. Under the action of the horizontally opposed airflow and heat, the central flow field of the vortex will point to the product collection module, which is helpful to improve product quality and preparation efficiency.

[0040] In addition, regarding the supply of catalyst, in some embodiments, the catalyst supply module includes an induction plasma unit, a catalyst precursor delivery unit and a catalyst growth unit that are arranged in conjunction with each other, the induction plasma unit is used to form a plasma torch, the catalyst precursor delivery unit is used to deliver catalyst precursor and inhibitor to the plasma torch, and the catalyst growth unit is used to make the catalyst precursor and inhibitor form catalyst particles under the action of the plasma torch, and the catalyst particles enter the reaction chamber driven by a third gas flow.

[0041] In some embodiments, the catalyst supply module is disposed on the top of the carbon nanotube growth chamber and is biased toward one side of the carbon source supply module, and the third direction forms an angle less than 90° with the first direction.

[0042] Regarding collecting products, in some embodiments, the product collection module includes a material outlet channel and a product collection module arranged at the top of the cavity wall of the carbon nanotube growth chamber. The single-walled carbon nanotubes formed in the vortex enter the material outlet channel driven by the flow field, and the product collection module collects the single-walled carbon nanotubes and discharges the exhaust gas.

[0043] As some typical examples of the above technical solutions, in actual processes, the device may include three chambers: a catalyst formation chamber, a carbon nanotube growth chamber, and a product collection chamber. The catalyst formation chamber includes an induction plasma unit, a catalyst precursor delivery unit, and a catalyst growth unit; the carbon nanotube growth chamber includes a counter-flow channel formed by vortex flow, an electric heating unit, a carbon source supply module, an etchant supply module, and a material outlet channel; the product collection chamber includes a gas-solid separation device and an exhaust gas treatment device.

[0044] The second aspect of the embodiment of the present invention also provides a two-step method for preparing single-walled carbon nanotubes, which comprises the following steps:

[0045] A first gas flow containing a carbon source is introduced into a reaction chamber in a first direction, a second gas flow containing an etchant is introduced into the reaction chamber in a second direction, and catalyst particles are introduced into the reaction chamber in a third direction, wherein the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow meet to form a vortex, and the third direction points to the vicinity of the location of the vortex;

[0046] The single-walled carbon nanotubes formed in the vortex and carried by the flow field of the vortex are collected above the vortex.

[0047] As some typical examples, the specific process flow of the above method is as follows: the first step is to use the induction plasma torch as a high-temperature heat source, and the catalyst precursor and the inhibitor are quickly evaporated and cracked at high temperature to form extremely fine nanoparticles, and the formed nanoparticles enter the growth chamber under the action of the airflow; the second step is to introduce a carbon source and an etchant into the growth chamber, control the reaction temperature, complete the cracking of the carbon source on the surface of the catalyst nanoparticles and the growth of carbon nanotubes, and enter the collection device upward along the airflow outlet, and finally realize the batch preparation of high-quality single-walled carbon nanotubes.

[0048] For more detailed equipment and process, please refer to Figure 1 As shown, the figure shows a device for preparing single-walled carbon nanotubes by a two-step method, which includes an induction plasma unit 1, a catalyst growth unit 2, a carbon source supply module 3, an etchant supply module 4, a carbon nanotube growth chamber 5, a material outlet channel 6 and a product collection unit 7.

[0049] The catalyst precursor and the inhibitor precursor enter the catalyst growth unit 2 through the induction plasma unit 1. Under the action of high temperature and the inhibitor, the catalyst precursor is evaporated, cracked and re-nucleated into nanoparticles with a size less than 10nm, and enters the carbon nanotube growth chamber 5 with the carrier gas; then, the carbon source enters the carbon nanotube growth chamber 5 with the carrier gas through the carbon source supply module 3, and the etchant enters the carbon nanotube growth chamber 5 with the carrier gas through the etchant supply module 4 to form a vortex, and completes the cracking, carburization, carbon precipitation and carbon tube growth of the carbon source on the surface of the catalyst nanoparticles; then, the product enters the material outlet channel 6 upward along the vortex outlet direction, and finally enters the product collection unit 7.

[0050] The actual process steps are as follows:

[0051] a. Expel the air from the reaction system, continuously introduce inert gas, adjust the input power of the induction plasma torch and start it, and set the temperature of the carbon tube growth chamber and start it, so that the catalyst formation chamber and the carbon tube growth chamber reach the desired reaction temperature;

[0052] b. introducing a mixture of a catalyst precursor and an inhibitor into the inlet of an induction plasma torch, so that the catalyst precursor evaporates completely and further grows to a nanometer size, and the nanoparticles enter the carbon tube growth chamber under the action of an inert gas flow;

[0053] c. A mixed gas flow of a carbon source and a carrier gas is quantitatively introduced into one side of the carbon tube growth chamber, and a mixed gas flow of an etchant and a carrier gas is quantitatively introduced into the other side, so that a vortex is formed in the second chamber. After the vortex contacts the catalyst particles, the carbon source is cracked on the surface of the catalyst particles and the carbon tubes grow;

[0054] d. Driven by the upward vortex airflow, the generated carbon tube products enter the collection system.

[0055] Regarding the specific details of the above method, in some embodiments, the carbon source includes any one or a combination of two or more of methanol, ethanol, toluene, acetone, ethylene, propylene, methane, ethane, and carbon monoxide, but is not limited thereto.

[0056] In some embodiments, the carrier gas of the first gas flow and / or the second gas flow includes any one of argon, helium, and nitrogen, or a combination of two or more thereof, but is not limited thereto.

[0057] In some embodiments, the etchant includes any one of water, hydrogen, and carbon dioxide, or a combination of two or more thereof, but is not limited thereto.

[0058] In some embodiments, the volume ratio of the carbon source to the carrier gas in the first gas flow is 1:0-100, and the volume ratio of the etchant to the carrier gas in the second gas flow is 1:0-100.

[0059] In some embodiments, the flow ratio of the first airflow to the second airflow is in the range of 0.01-1: 1. The flow ratio of the first airflow to the second airflow has a certain influence on the formation of the vortex, and usually the ratio of the two is about 0.5-1: 1, but even if it reaches the range of 0.01: 1, the vortex effect can be formed.

[0060] In some embodiments, the catalyst particles are formed from a catalyst precursor and an inhibitor under the action of a plasma torch, and the temperature of the plasma torch is 3000-30000°C.

[0061] In some embodiments, the temperature in the reaction chamber is 800-1500°C;

[0062] In some embodiments, the catalyst precursor includes any one or a combination of two or more of ferrocene, ferrous chloride, ferric chloride, ferric sulfate, iron, iron oxide, cobalt, cobalt chloride, cobalt sulfate, nickel, nickel chloride, and nickel sulfate; the inhibitor includes any one or a combination of two or more of thiophene, dimethyl sulfoxide, thiourea, sulfur, sodium sulfate, sodium sulfide, and iron sulfide, but is not limited thereto.

[0063] In some embodiments, the polymerization inhibitor includes any one or a combination of two or more of thiophene, dimethyl sulfoxide, thiourea, sulfur, sodium sulfate, sodium sulfide, and iron sulfide, but is not limited thereto.

[0064] In some embodiments, the molar ratio of the catalyst precursor to the polymerization inhibitor is 1:0.001-5.

[0065] In some embodiments, the single-walled carbon nanotubes prepared by the method can have a product purity of 70-85%, a G / D ratio greater than 30, an output of 1-10 kg / day, and can achieve continuous batch processing, which has important commercial application value.

[0066] It should be noted that the above-mentioned specific technical details are some exemplary details for realizing the preparation of single-walled carbon nanotubes in the present invention, which mainly serve as a reference for those skilled in the art, and do not mean that the scope of implementation based on the core idea of ​​the present invention is limited to this. The devices designed or methods adopted based on the key concept of the present invention are all within the feasible scope, and the specific reaction materials and conditions therein can refer to the precedents of single-walled carbon nanotube growth mentioned in many prior arts or develop new reaction materials and conditions by oneself.

[0067] The above technical solution adopts the induction plasma arc method to provide ultra-high energy for the preparation of nanocatalysts, greatly improving the decomposition efficiency of catalyst precursors; by utilizing a two-step process to separate the preparation process of catalyst nanoparticles from the carbon tube growth process, the controllable preparation of catalyst nanoparticles and the orderly separation of the carbon tube growth steps are achieved, reducing the influence of mixed variables on the reaction; by designing an optimized reaction chamber and air flow size, the residence time of the catalyst and the cracking efficiency of the carbon source are effectively controlled; by introducing a vortex in the carbon tube growth chamber, the outlet direction of the vortex flow field is uniform, so that the carbon tube product can be discharged from the reaction chamber in time, realizing long-term continuous preparation.

[0068] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0069] Example 1

[0070] This embodiment illustrates a two-step process for preparing single-walled carbon nanotubes, which comprises:

[0071] Step 1: The air in the reaction system is evacuated by a vacuum pump and filled with helium. The induction plasma device is started to ignite the arc, and the electric heating device of the carbon nanotube growth chamber is turned on at the same time, and the temperature is set to 1200°C.

[0072] Step 2: After reaching the set temperature, ferrocene (20 g / min) and thiophene (5 g / min) are introduced into the inlet of the induction plasma unit. Ferrocene and thiophene are completely evaporated and cracked, and then further grow to nanometer size. The nanoparticles enter the carbon nanotube growth chamber under the action of inert gas flow.

[0073] Step 3: A mixture of propylene (40 L / min) and helium (200 L / min) is input through the carbon source supply module, and a mixture of hydrogen (40 L / min) and helium (200 L / min) is input through the etchant supply module to form a vortex in the carbon nanotube growth chamber. With the introduction of the carbon source, black carbon nanotube products are generated instantly under the action of the catalyst.

[0074] Step 4: The product then enters the product collector through the material outlet, and the gas is discharged after passing through the tail gas treatment device.

[0075] After the reaction is completed, take an appropriate amount of sample for characterization. The microscopic morphology, size, crystallinity and carbon content of single-walled carbon nanotubes are measured by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and thermogravimetry, respectively. For specific characterization methods, refer to GB / T 32869-2016, GB / T 30534-2014, GB / T 32871-2016 and GB / T 24490-2009.

[0076] The characterization results are as follows Figure 2-5 As shown. Thermogravimetric characterization results show that the prepared single-walled carbon nanotubes have a carbon content of 78 wt%. In the Raman spectrum ( Figure 4 ), respectively at 1570cm -1 、1350cm -1 and 0-200cm -1 The band shows a sharp graphite peak (G band), an unusually small disorder peak (D band) and a highly obvious radial breathing mode characteristic peak RBM. The G / D ratio is 52.2, indicating a high degree of crystallinity of the carbon nanotubes. In the high-resolution transmission electron microscopy characterization results ( Figure 3 ), it can be seen that the size of the catalyst particles is 3-5nm.

[0077] Comparative Example 1

[0078] This comparative example is substantially the same as Example 1, except that:

[0079] The etchant supply module is turned off, and a mixture of hydrogen (40L / min) and helium (200L / mm) is mixed with the original carbon source gas flow (propylene (40L / min) and helium (200L / min)) from the channel of the original carbon source supply module and injected into the reaction chamber.

[0080] The other reaction conditions and reaction materials are consistent with those in Example 1.

[0081] In this comparative example, since the etchant and the carbon source are introduced together in the same direction, the etchant can take effect at the initial stage of the cracking reaction of the carbon source, interfering with the formation process of the carbon nanotubes. In addition, this co-directional airflow is difficult to form a vortex, resulting in stagnation in some corners of the reaction chamber. The stagnation spreads everywhere, which also affects the formation process of the carbon nanotubes. The stagnation itself is also an impurity. Therefore, the obtained product cannot be discharged in time, and the reaction chamber is blocked in large quantities, resulting in the inability to produce continuously.

[0082] Comparative Example 2

[0083] This comparative example is substantially the same as Example 1, except that:

[0084] The induction plasma coil of the catalyst supply module is arranged outside the pipeline of the carbon source supply module, and the catalyst, the polymerization inhibitor and the corresponding inert gas are combined with the carbon source gas flow and then passed through the induction plasma coil and then introduced into the reaction chamber.

[0085] The other reaction conditions and reaction materials are consistent with those in Example 1.

[0086] In this comparative example, since the formation process of the catalyst particles was mixed with the carbon source too early, the growth of the catalyst particles was disturbed, the influencing variables increased sharply, and it was difficult to control stability. Therefore, the G / D ratio and purity of the obtained product were significantly lower. Figure 6 , Figure 7 As shown, the G / D ratio is only about 10, and the TG residue reaches 112%, which is far from the industrial requirements.

[0087] Comparative Example 3

[0088] This comparative example is substantially the same as Example 1, except that:

[0089] The catalyst supply module is arranged on a side biased toward the etchant supply module, and is still directed to the vicinity of the position where the vortex is formed (ie, below the material outlet).

[0090] The other reaction conditions and reaction materials are consistent with those in Example 1.

[0091] In this comparative example, since the catalyst particles first meet the etchant and then meet the carbon source, the effect of the etchant does not occur after the carbon source and the catalyst particles contact and react. Therefore, the G / D ratio and purity of the obtained product are reduced. Figure 8 , Fig. 9 As shown, the product can still be discharged continuously.

[0092] Example 2

[0093] A two-step method for preparing single-walled carbon nanotubes comprises:

[0094] Step 1: The air in the reaction system is evacuated by a vacuum pump and filled with argon. The induction plasma device is started to ignite the arc, and the electric heating device of the carbon nanotube growth chamber is turned on at the same time, and the temperature is set to 1500°C.

[0095] Step 2: After reaching the set temperature, cobalt powder (20 g / min), iron powder (20 g / min), and thiourea (5 g / min) are introduced into the inlet of the induction plasma unit. The cobalt powder, iron powder, and thiourea are completely evaporated and cracked, and then further grow to nano size. The nanoparticles enter the carbon tube growth chamber under the action of an inert gas flow.

[0096] Step 3: A mixed gas of methane (50 L / min) and argon (400 L / min) is input through the carbon source supply module, and a mixed gas of water (10 L / min) and helium (500 L / min) is input through the etchant supply module to form a vortex in the carbon nanotube growth chamber. With the introduction of the carbon source, black carbon nanotube products are generated instantly under the action of the catalyst.

[0097] Step 4: The product then enters the product collector through the material outlet, and the gas is discharged after passing through the tail gas treatment device.

[0098] The obtained product is similar to that in Example 1, having the characteristics of high purity and high crystallinity, and also having excellent stability during continuous batch preparation.

[0099] Example 3

[0100] A two-step method for preparing single-walled carbon nanotubes comprises:

[0101] Step 1: The air in the reaction system is evacuated by a vacuum pump and filled with nitrogen. The induction plasma device is started to strike the arc, and the electric heating device of the carbon nanotube growth chamber is turned on at the same time, and the temperature is set to 1000°C.

[0102] Step 2: After reaching the set temperature, nickel powder (10 g / min), ferrocene (30 g / min) and thiourea (10 g / min) are introduced into the inlet of the induction plasma unit. The nickel powder, ferrocene and thiourea are completely evaporated and cracked, and then further grow to nano size. The nanoparticles enter the carbon tube growth chamber under the action of inert gas flow.

[0103] Step 3: A mixed gas of ethanol (0.1 L / min) and nitrogen (300 L / min) is input through the carbon source supply module, and a mixed gas of hydrogen (20 L / min), water (0.05 L / min) and nitrogen (400 L / min) is input through the etchant supply module to form a vortex in the carbon nanotube growth chamber. With the introduction of the carbon source, black carbon nanotube products are generated instantly under the action of the catalyst.

[0104] Step 4: The product then enters the product collector through the material outlet, and the gas is discharged after passing through the tail gas treatment device.

[0105] The obtained product is similar to that in Example 1, having the characteristics of high purity and high crystallinity, and also having excellent stability during continuous batch preparation.

[0106] Example 4

[0107] A two-step method for preparing single-walled carbon nanotubes comprises:

[0108] Step 1: The air in the reaction system is evacuated by a vacuum pump and filled with argon. The induction plasma device is started to strike the arc, and the electric heating device of the carbon nanotube growth chamber is turned on at the same time, and the temperature is set to 1400°C.

[0109] Step 2: After reaching the set temperature, iron oxide (20 g / min) and thiophene (10 g / min) are introduced into the inlet of the induction plasma unit. The iron oxide and thiophene are completely evaporated and cracked, and then further grow to nano size. The nanoparticles enter the carbon tube growth chamber under the action of inert gas flow.

[0110] Step 3: A mixed gas of methane (40 L / min) and argon (200 L / min) is input through the carbon source supply module, and a mixed gas of hydrogen (40 L / min), water (0.01 L / min) and argon (200 L / min) is input through the etchant supply module to form a vortex in the carbon nanotube growth chamber. With the introduction of the carbon source, black carbon nanotube products are generated instantly under the action of the catalyst.

[0111] Step 4: The product then enters the product collector through the material outlet, and the gas is discharged after passing through the tail gas treatment device.

[0112] The obtained product is similar to that in Example 1, having the characteristics of high purity and high crystallinity, and also having excellent stability during continuous batch preparation.

[0113] Based on the above embodiments and comparative examples, it can be clearly seen that the preparation device and method provided by the present invention avoid the mutual interference phenomenon that occurs in the early stage of the reaction in the traditional preparation method by introducing the catalyst, carbon source and etchant into the reaction chamber through different channels, especially avoids the mutual interference between the carbon source and the catalyst, provides a controllable and stable catalyst particle formation process, realizes the controllable preparation of catalyst nanoparticles and the orderly separation of the carbon nanotube growth steps, and reduces the influence of mixed variables on the reaction; in addition, the opposite intersection of the carbon source gas flow and the etchant gas flow is used to form a vortex, and the vortex avoids the problem of local sedimentation and blockage of the tangential laminar flow, thereby avoiding the influence on the quality and continuous growth of the carbon nanotubes, and finally realizes the large-scale preparation of high-purity and high-crystallinity single-walled carbon nanotubes.

[0114] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-step method for preparing single-walled carbon nanotubes, characterized in that: include: A carbon nanotube growth chamber, a product collection module, a catalyst supply module, a carbon source supply module, and an etchant supply module; The product collection module, catalyst supply module, carbon source supply module and etchant supply module are fixedly mounted on the cavity wall of the carbon nanotube growth chamber and are in communication with the internal reaction chamber of the carbon nanotube growth chamber; The carbon source supply module is used to pass a first gas flow containing a carbon source into the reaction chamber in a first direction, and the etchant supply module is used to pass a second gas flow containing an etchant into the reaction chamber in a second direction, and the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow converge to form a vortex; the catalyst supply module is used to pass catalyst particles into the reaction chamber in a third direction, and the third direction points to the vicinity of the position of the vortex; the product collection module is arranged above the vortex, and is used to collect single-walled carbon nanotubes formed in the vortex.

2. The device according to claim 1, characterized in that The carbon source supply module is disposed on one side of the carbon nanotube growth chamber, the etchant supply module is disposed on the other side opposite to the carbon nanotube growth chamber, and the first direction and the second direction are both disposed horizontally and both point to the center of the vortex.

3. The device according to claim 2, characterized in that The carbon nanotube growth chamber is also provided with a heating unit for adjusting the temperature in the reaction chamber. Directly below the product collection module, the vortex forms a vertically upward flow field under the influence of heat.

4. The device according to claim 1, characterized in that The catalyst supply module includes an induction plasma unit, a catalyst precursor delivery unit and a catalyst growth unit that are arranged in coordination. The induction plasma unit is used to form a plasma torch. The catalyst precursor delivery unit is used to deliver catalyst precursors and inhibitors to the plasma torch. The catalyst growth unit is used to form catalyst particles from the catalyst precursors and inhibitors under the action of the plasma torch. The catalyst particles enter the reaction chamber driven by a third gas flow.

5. The device according to claim 1 or 4, characterized in that: The catalyst supply module is disposed on the top of the carbon nanotube growth chamber and is biased toward one side of the carbon source supply module. The third direction forms an angle less than 90° with the first direction.

6. The device according to claim 1, characterized in that The product collection module includes a material outlet channel and a product collection module arranged at the top of the cavity wall of the carbon nanotube growth chamber. The single-walled carbon nanotubes formed in the vortex enter the material outlet channel driven by the flow field. The product collection module collects the single-walled carbon nanotubes and discharges the tail gas.

7. A two-step method for preparing single-walled carbon nanotubes, characterized in that: include: A first gas flow containing a carbon source is introduced into a reaction chamber in a first direction, a second gas flow containing an etchant is introduced into the reaction chamber in a second direction, and catalyst particles are introduced into the reaction chamber in a third direction, wherein the first direction and the second direction are opposite to each other so that the first gas flow and the second gas flow meet to form a vortex, and the third direction points to the vicinity of the location of the vortex; The single-walled carbon nanotubes formed in the vortex and carried by the flow field of the vortex are collected above the vortex.

8. The method according to claim 7, characterized in that The carbon source includes any one or a combination of two or more of methanol, ethanol, toluene, acetone, ethylene, propylene, methane, ethane, and carbon monoxide; and / or, the carrier gas of the first gas flow and / or the second gas flow comprises any one of argon, helium, and nitrogen, or a combination of two or more thereof; And / or, the etchant includes any one of water, hydrogen, and carbon dioxide, or a combination of two or more thereof; and / or, the volume ratio of the carbon source to the carrier gas in the first gas flow is 1:0-100, and the volume ratio of the etchant to the carrier gas in the second gas flow is 1:0-100; And / or, the flow ratio of the first airflow to the second airflow is 0.01-1:

1.

9. The method according to claim 7, characterized in that: The catalyst particles are formed by a catalyst precursor and an inhibitor under the action of a plasma torch, and the temperature of the plasma torch is 3000-30000°C; and / or, the temperature in the reaction chamber is 800-1500° C.; Preferably, the catalyst precursor includes any one or a combination of two or more of ferrocene, ferrous chloride, ferric chloride, ferric sulfate, iron, ferric oxide, cobalt, cobalt chloride, cobalt sulfate, nickel, nickel chloride, and nickel sulfate; the inhibitor includes any one or a combination of two or more of thiophene, dimethyl sulfoxide, thiourea, sulfur, sodium sulfate, sodium sulfide, and iron sulfide; And / or, the polymerization inhibitor includes any one or a combination of two or more of thiophene, dimethyl sulfoxide, thiourea, sulfur, sodium sulfate, sodium sulfide, and iron sulfide; And / or, the molar ratio of the catalyst precursor to the polymerization inhibitor is 1:0.0015.

10. The method according to claim 7, characterized in that The single-walled carbon nanotubes prepared by the method can have a product purity of 70-85%, a G / D ratio greater than 30, and an output of 1-10 kg / day.

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