Dual-channel catalyst introduction system and method for continuous production of carbon nanotubes by combustion method

Abstract

The application belongs to the technical field of carbon nanotube preparation, and discloses a double-channel catalyst introduction system and method for continuously preparing carbon nanotubes by combustion method. The system comprises a catalyst gasification device, a promoter screening gasification device, a coaxial mixing device, and a gas path and a control unit. The catalyst gasification device mixes the metal organic precursor solution after being heated and gasified with the carrier gas; the promoter screening gasification device atomizes the sulfur-containing promoter solution by electrospray, removes large droplets by impact classification, and converts the solution into quasi-gas phase flow by secondary evaporation; the two are uniformly mixed in the central channel of the coaxial mixing device, and inert gas is introduced into the outer annular channel for flow protection. The application independently processes and accurately controls through double-channel branch, effectively avoids catalyst agglomeration and uneven introduction of promoters, significantly improves the diameter uniformity and purity of carbon nanotubes, and has the advantages of continuous and large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of carbon nanotube preparation technology, specifically relating to a dual-channel catalyst introduction system and method for continuous preparation of carbon nanotubes by combustion. Background Technology

[0002] Carbon nanotubes (CNTs) possess significant application value in energy storage devices, catalyst supports, electronic devices, and functional composite materials due to their excellent electrical, mechanical, and thermal properties. Existing preparation methods include arc discharge, laser ablation, chemical vapor deposition, and combustion methods, among which combustion methods are gaining increasing attention due to their high energy utilization, simple process, high yield, and potential for continuous production. In combustion synthesis, the catalyst introduction method directly determines the nucleation density, diameter distribution, and structural quality of the CNTs. Current technologies typically employ a single-channel injection method, pre-mixing the organometallic precursor (such as ferrocene) with the carbon source and inert diluent gas before introducing it into the combustion chamber. For example, Chinese patent CN102115075A discloses a frustum-shaped flame burner and its method for synthesizing CNTs, in which the reaction mixture, metal catalyst nanoparticles, and inert gas are mixed in a central premixing chamber before entering the reaction zone. However, this pre-mixed introduction method has the following problems: catalyst particles are prone to agglomeration in the high-temperature combustion field, resulting in uneven distribution of the diameter of the generated carbon nanotubes; the catalyst concentration is difficult to control independently, affecting the stability of product quality.

[0003] Furthermore, existing studies have shown that appropriate amounts of sulfur-containing promoters (such as thiophene) can significantly improve the nucleation and growth behavior of carbon nanotubes, increasing the proportion of straight tubes and the yield. However, existing promoter introduction methods are generally quite simple, mostly involving direct mixing or simple steam introduction. Limited by evaporation characteristics and transport efficiency, it is difficult to achieve precise control of concentration and distribution. For example, Chinese patent CN201811445735X discloses a method for controllably preparing single-walled carbon nanotubes without sulfur impurities using a growth promoter. This method uses an ultrasonic atomization device to introduce a mixed solution containing a catalyst precursor and a growth promoter precursor into a reactor. However, since the catalyst and promoter are pre-dissolved in the same solution, their introduction rates and concentrations cannot be independently controlled, resulting in significant fluctuations in product quality.

[0004] Therefore, there is an urgent need to develop a new catalyst introduction system and method to ensure the stability and rationality of the reaction field by separately supplying and independently controlling the carbon source, catalyst and promoter, thereby achieving the continuous preparation of high-quality and highly uniform carbon nanotubes. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a dual-channel catalyst introduction system and method for the continuous preparation of carbon nanotubes by combustion, which aims to overcome the problems of uneven catalyst dispersion, unstable introduction of promoters, and difficulty in independently controlling key reaction parameters in the existing combustion method for preparing carbon nanotubes.

[0006] To achieve the aforementioned objectives, the technical solution adopted is as follows: Therefore, the purpose of this invention is to provide a dual-channel catalyst introduction system and method for the continuous preparation of carbon nanotubes by combustion, which aims to overcome the problems of uneven catalyst dispersion, unstable introduction of promoters, and difficulty in independently controlling key reaction parameters in the existing combustion method for preparing carbon nanotubes.

[0007] To achieve the aforementioned objectives, the technical solution adopted is as follows: A dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes includes: The catalyst gasification device includes a first injection pump, a carrier gas branch and a heated gasifier connected thereto, for fully vaporizing the metal-organic precursor solution through the heated gasifier and mixing it with the carrier gas to form a catalyst gas phase flow. The accelerator screening and vaporization device includes a second injection pump, an electro-spray atomizer, an impact classifier, and a secondary evaporation tube connected thereto. It is used to atomize the sulfur-containing accelerator solution into fine droplets through the electro-spray atomizer, remove large droplets with a particle size greater than the critical particle size through the impact classifier, and then heat and convert it into a quasi-gas phase flow through the secondary evaporation tube. Quasi-gas phase flow: This refers to a process where, after secondary evaporation, the particle size of the accelerator droplets is significantly reduced (D50 < 5 μm), most of the solvent has evaporated, and the accelerator is suspended in the carrier gas as extremely fine droplets or molecular clusters. Its physical state is between the gas and liquid phases, exhibiting similar flowability and dispersibility to the gas phase, but not yet fully reaching the molecular-level gaseous state. Accelerators in this state can be uniformly dispersed in the combustion field, avoiding localized concentration unevenness caused by the presence of large droplets.

[0008] Impact classifier: An aerosol particle size separation device based on the principle of inertial impact. When the airflow carrying droplets is accelerated through the nozzle and impacts the collecting plate, large-diameter droplets are captured due to their greater inertia, while small-diameter droplets continue to move forward with the airflow around the collecting plate, thus achieving particle size classification.

[0009] A coaxial mixing device includes a coaxial sleeve structure consisting of an inner tube and an outer tube. The inlet end of the inner tube is connected to the outlet of the heating gasifier and the outlet of the secondary evaporation tube, respectively. A central channel is formed inside the inner tube for uniformly mixing the catalyst gas phase flow and the promoter quasi-gas phase flow. An outer annular channel is formed between the inner tube and the outer tube for introducing an inert gas to protect the flow. The gas path and control unit includes a mass flow meter and a PID control module, which are used to independently control the introduction rate of the catalyst and the promoter. The mass flow meter is installed in the carrier gas branch and the inert gas protection pipeline, respectively. The PID control module is connected to the first injection pump, the second injection pump, the heated gasifier, the electro-spray atomizer, the secondary evaporation tube and the mass flow meter, respectively, and is used to independently adjust the feed rate, gasification temperature, atomization voltage, evaporation temperature and gas flow rate of the catalyst precursor and the sulfur-containing promoter.

[0010] As a further improvement of the present invention, the injection speed of the first injection pump is 1 to 10 mL / min, and the temperature of the heating belt vaporizer is 100 to 300°C.

[0011] As a further improvement of the present invention, the injection speed of the second injection pump is 0.5 to 5 mL / min, and the frequency of the electro-spray atomizer is 0.5 to 5 MHz.

[0012] As a further improvement of the present invention, the critical particle size for the impact classifier is 5 μm.

[0013] As a further improvement of the present invention, the temperature of the secondary evaporation tube is 200°C.

[0014] As a further improvement of the present invention, the carrier gas branch gas is nitrogen, and the flow rate is 0.3 to 3 L / min.

[0015] As a further improvement of the present invention, the inert gas in the outer annular channel is argon, and the flow rate is 2 to 10 L / min.

[0016] A method for the continuous preparation of carbon nanotubes using a combustion method with a system as described in any of the preceding claims, comprising the following steps: (a) The metal-organic precursor solution is fed into the heated gasifier at a set rate through the first injection pump. After being fully vaporized at 100-300°C, it is mixed with the carrier gas to form a catalyst gas phase flow. (b) The sulfur-containing accelerator solution is fed into the electrospray atomizer at a set rate through the second injection pump and atomized into fine droplets. After the droplets are removed by the impact classifier to remove large droplets with a particle size greater than 5 μm, they enter the secondary evaporation tube and are converted into a quasi-gas phase flow at 200°C. (c) The catalyst gas phase flow obtained in step (a) and the promoter quasi-gas phase flow obtained in step (b) are respectively introduced into the central channel of the coaxial mixing device for uniform mixing, while an inert gas is introduced through the outer annular channel to carry out the flow. (d) The mixed gas phase flow enters the combustion reaction zone and carbon nanotubes are continuously synthesized under flame conditions.

[0017] As a further improvement of the present invention, the organometallic precursor is ferrocene, the solvent is ethanol, and the solution concentration is 5-20 mg / mL; the sulfur-containing accelerator is thiophene, the solvent is ethanol, and the volume fraction is 0.1%-2%.

[0018] As a further improvement of the present invention, the combustion reaction is carried out under low-pressure premixed flame conditions, with an oxygen flow rate of 1 to 5 L / min and a combustion chamber pressure of 50 to 60 kPa.

[0019] The beneficial effects of this invention are: Dual-channel independent control avoids agglomeration and uneven distribution: This invention employs a dual-channel, separate introduction design, allowing the catalyst and accelerator to undergo optimized treatment before entering the combustion field. The catalyst is fully vaporized and uniformly dispersed through a heated vaporizer, while the accelerator undergoes a three-stage treatment—electrospray atomization, impact grading, and secondary evaporation—to ensure stable introduction in a quasi-gas phase, effectively avoiding catalyst agglomeration and uneven accelerator distribution problems caused by a single injection method.

[0020] Accelerator particle size is precisely controllable: micro-droplets are generated by an electro-spray atomizer, large droplets (>5μm) are removed by an impact classifier, and the solvent is further evaporated by a secondary evaporation tube, so that the accelerator is introduced in a uniform quasi-gas phase flow form, which significantly improves the uniformity of accelerator distribution in the combustion field.

[0021] 3. Coaxial mixing and flow protection design to improve reaction stability: The coaxial mixing device adopts a structural design with a central channel for mixing the reaction material and an outer annular channel for introducing inert gas to protect the flow. This not only improves the mixing efficiency of the catalyst and the promoter, but also isolates the central reaction zone from the interference of the external environment through the inert gas flow protection, suppresses turbulent disturbances, thereby improving the stability of the reaction field and effectively suppressing the generation of amorphous carbon and soot.

[0022] 4. Independent and precise control: The introduction rate of catalyst and accelerator is independently controlled by the PID control module and mass flow meter, respectively. The ratio can be flexibly adjusted according to different application requirements to achieve stable production of high-yield and high-purity carbon nanotubes.

[0023] 5. Continuous preparation capability: The system of the present invention has good continuous preparation capability and can flexibly adjust the type and ratio of promoters according to different application requirements, thereby achieving stable production of carbon nanotubes with high yield and high purity.

[0024] 6. Broad Application Prospects: The carbon nanotubes prepared by this invention have advantages such as uniform diameter, high purity, and a high proportion of straight tubes. The type and ratio of accelerators can be flexibly adjusted according to different application requirements to achieve stable production of high-yield, high-purity carbon nanotubes. The system and method described in this invention not only overcome the shortcomings of existing technologies but also demonstrate significant advantages in the quality control, uniformity improvement, and continuous production of carbon nanotubes. It is suitable for large-scale industrial production and has broad application prospects. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the dual-channel catalyst introduction system for preparing carbon nanotubes by combustion method according to the present invention. Figure 2 This is a schematic diagram illustrating the working principle of the impact classifier in this invention; Figure 3 This is a TEM image of the carbon nanotubes prepared in Example 1 of the present invention; Figure 4 This is a TEM image of the carbon nanotubes prepared in Example 2 of the present invention; Figure 5 This is a TEM image of the carbon nanotubes prepared in Example 3 of the present invention; Figure 6 This is a TEM image of the carbon nanotubes prepared in the comparative example of this invention.

[0026] In the diagram: 1. First injection pump; 2. Carrier gas branch; 3. Heated vaporizer; 4. Second injection pump; 5. Electro-spray atomizer; 6. Impact classifier; 7. Secondary evaporation tube; 8. Coaxial mixing device; 9. Central channel; 10. Outer annular channel. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] Example 1

[0030] Construct a dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes as described in this invention, the system comprising: The catalyst gasification device includes a first injection pump 1, a carrier gas branch 2 and a heated gasifier 3 connected in sequence, which are used to fully vaporize the metal-organic precursor solution through the heated gasifier 3 and mix it with the carrier gas to form a catalyst gas phase flow. The accelerator screening and vaporization device includes a second injection pump 4, an electro-spray atomizer 5, an impact classifier 6 and a secondary evaporation tube 7 connected in sequence. It is used to atomize the sulfur-containing accelerator solution into fine droplets through the electro-spray atomizer 5, remove large droplets with a particle size greater than the critical particle size through the impact classifier 6, and then heat and convert it into a quasi-gas phase flow through the secondary evaporation tube 7. The coaxial mixing device 8 includes a coaxial sleeve structure consisting of an inner tube and an outer tube. The inlet end of the inner tube is connected to the outlet of the heated vaporizer 3 and the outlet of the secondary evaporation tube 7, respectively. A central channel 9 is formed inside the inner tube for uniformly mixing the catalyst gas phase flow and the promoter quasi-gas phase flow. An outer annular channel 10 is formed between the inner and outer tubes for introducing an inert gas to protect the flow. This invention employs a three-stage series process of electro-spray atomization → impact classification → secondary evaporation. The electro-spray atomizer 5 generates micron-sized droplets, the impact classifier 6 retains large droplets with a particle size greater than 5 μm, and the secondary evaporation tube 7 converts the remaining fine droplets into a quasi-gas phase flow at 200°C. This "quasi-gas phase flow" combines the uniform dispersion of the gas phase with the controllable concentration of the liquid phase, achieving precise quantitative introduction of the promoter in the combustion zone. The catalyst gas phase flow and the promoter quasi-gas phase flow are premixed in the central channel 9 before entering the combustion reaction zone, which avoids uneven mixing caused by violent reaction in the combustion zone; the inert gas escort in the outer annular channel 10 further stabilizes the reaction field and inhibits the generation of amorphous carbon and soot.

[0031] The gas path and control unit includes a mass flow meter and a PID control module, which are used to independently control the introduction rate of the catalyst and the promoter. The mass flow meter is installed in the carrier gas branch 2 and the inert gas shielding pipeline. The PID control module is connected to the first injection pump 1, the second injection pump 4, the heating belt vaporizer 3, the electro-spray atomizer 5, the secondary evaporation tube 7 and the mass flow meter, respectively, and is used to independently adjust the feed rate, vaporization temperature, atomization voltage, evaporation temperature and gas flow rate of the catalyst precursor and the sulfur-containing promoter.

[0032] The specific process parameters and operating procedures are as follows: 1) In the catalyst gasification device, the first injection pump 1 is used to deliver a ferrocene / ethanol solution with a concentration of 5 mg / mL and a flow rate of 1 mL / min. After being completely vaporized at 100°C by the heated gasifier 3, it is mixed with nitrogen carrier gas at a flow rate of 0.3 L / min to form a catalyst gas phase flow.

[0033] 2) In the accelerator screening vaporization device, the second injection pump 4 is used to deliver a 0.5% volume fraction thiophene / ethanol solution at a flow rate of 0.5 mL / min. The solution is atomized into fine droplets by the electro-spray atomizer 5 (frequency 0.5 MHz). After the droplets pass through the impact classifier 6 (critical particle size of 5 μm) to remove large droplets, they enter the secondary evaporation tube 7 and are converted into a quasi-gas phase flow at 200°C.

[0034] 3) The catalyst gaseous flow and the promoter quasi-gaseous flow are uniformly mixed in the central channel 9 of the coaxial mixing device 8, while argon gas at a flow rate of 2 L / min is introduced into the outer annular channel 10. The system operates under low-pressure premixed flame conditions, with an oxygen flow rate of 2 L / min and a combustion chamber pressure of 50 kPa.

[0035] Product characterization: Figure 3 This is a TEM image of the carbon nanotubes prepared in this embodiment. Figure 3 It can be seen that the obtained carbon nanotubes are mainly single-walled tubes with uniform diameter, narrow tube diameter distribution, low amorphous carbon content, and high purity.

[0036] Example 2

[0037] A dual-channel catalyst introduction system for the continuous preparation of carbon nanotubes by combustion as described in this invention is constructed. The system structure is the same as in Example 1, including a catalyst gasification device, a promoter screening gasification device, a coaxial mixing device 8, and a gas path and control unit. The connection method and function of each component are the same as described in Example 1.

[0038] The specific process parameters and operating procedures are as follows: 1) In the catalyst gasification device, the first injection pump 1 is used to deliver a ferrocene / ethanol solution with a concentration of 10 mg / mL and a flow rate of 5 mL / min. After being completely vaporized at 200°C by the heated gasifier 3, it is mixed with nitrogen carrier gas at a flow rate of 2 L / min to form a catalyst gas phase flow.

[0039] 2) In the accelerator screening and vaporization device, the second injection pump 4 is used to deliver a 0.5% volume fraction thiophene / ethanol solution at a flow rate of 3 mL / min. The solution is atomized into fine droplets by an electro-spray atomizer 5 (frequency 3 MHz). After the droplets pass through an impact classifier 6 (critical particle size of 5 μm) to remove large droplets, they enter the secondary evaporation tube 7 and are converted into a quasi-gas phase flow at 200°C.

[0040] 3) The catalyst gas phase flow and the promoter quasi-gas phase flow are uniformly mixed in the central channel 9 of the coaxial mixing device 8, and argon gas at a flow rate of 6 L / min is introduced into the outer annular channel 10. The system operates under low-pressure premixed flame conditions, with an oxygen flow rate of 2 L / min and a combustion chamber pressure of 55 kPa.

[0041] Product characterization: Figure 4 This is a TEM image of the carbon nanotubes prepared in this embodiment. Figure 4 It can be seen that the resulting carbon nanotubes are generally uniformly distributed, but due to the high catalyst injection rate and gasification temperature, some carbon nanotubes show a trend of increasing diameter and multi-walled structure, and the product is mainly a mixture of single-walled and double-walled tubes.

[0042] Example 3

[0043] A dual-channel catalyst introduction system for the continuous preparation of carbon nanotubes by combustion as described in this invention is constructed. The system structure is the same as in Example 1, including a catalyst gasification device, a promoter screening gasification device, a coaxial mixing device 8, and a gas path and control unit. The connection method and function of each component are the same as described in Example 1.

[0044] The specific process parameters and operating procedures are as follows: 1) In the catalyst gasification device, the first injection pump 1 is used to deliver a ferrocene / ethanol solution with a concentration of 20 mg / mL and a flow rate of 10 mL / min. After being completely vaporized at 300°C by the heated gasifier 3, it is mixed with nitrogen carrier gas at a flow rate of 3 L / min to form a catalyst gas phase flow.

[0045] 2) In the accelerator screening vaporization device, the second injection pump 4 is used to deliver a 2.0% thiophene / ethanol solution at a flow rate of 5 mL / min. The solution is atomized into fine droplets by the electro-spray atomizer 5 (frequency 5 MHz). After the droplets pass through the impact classifier 6 (critical particle size of 5 μm) to remove large droplets, they enter the secondary evaporation tube 7 and are converted into a quasi-gas phase flow at 200°C.

[0046] 3) The catalyst gas phase flow and the promoter quasi-gas phase flow are uniformly mixed in the central channel 9 of the coaxial mixing device 8, and argon gas at a flow rate of 10 L / min is introduced into the outer annular channel 10. The system operates under low-pressure premixed flame conditions, with an oxygen flow rate of 2 L / min and a combustion chamber pressure of 60 kPa.

[0047] Product characterization: Figure 5 This is a TEM image of the carbon nanotubes prepared in this embodiment. Figure 5 It can be seen that the obtained carbon nanotubes are mainly multi-walled tubes with relatively large diameters, and some areas exhibit graphite layer accumulation and amorphous carbon coating. This example shows that excessively high catalyst concentration and temperature are beneficial to the growth of multi-walled carbon nanotubes.

[0048] Comparative Example 1 A single-channel preparation apparatus was constructed, without employing the dual-channel catalyst introduction system described in this invention. Specific conditions are as follows: 1) Ferrocene and thiophene were directly dissolved in ethanol at a concentration of 10 mg / mL and a thiophene volume fraction of 0.5%. The solution was then directly fed into a heated vaporizer at a rate of 2 mL / min using a syringe pump. The heating temperature was 200°C. After vaporization, the solution was mixed with nitrogen gas at a rate of 5 L / min. 2) The resulting mixed gas flow is directly introduced into the central channel of the injection head without undergoing impact classification and secondary evaporation treatment; 3) Argon gas is introduced into the outer ring at a flow rate of 6L / min. The system operates under low-pressure premixed flame conditions, with an oxygen flow rate of 2L / min and a combustion chamber pressure of 55kPa.

[0049] Figure 6 This is a TEM image of the carbon nanotubes prepared in this comparative example, by... Figure 6 It can be seen that the diameter distribution of the obtained carbon nanotubes is uneven, and the product contains a large number of amorphous carbon and aggregated particles. Compared with Example 1, the purity and structural integrity of the product are significantly reduced, indicating that the lack of dual-channel independent processing and staged evaporation will seriously affect the formation quality of carbon nanotubes.

[0050] This invention employs an independent dual-channel design, where the organometallic precursor (catalyst) and sulfur-containing accelerator are separately optimized before entering the combustion chamber. The catalyst channel utilizes a heated vaporizer for thorough vaporization and uniform dispersion; the accelerator channel employs a combination of electrospray atomization, impact classification, and secondary evaporation to convert the liquid-phase accelerator into a quasi-gas phase flow with uniform particle size. The two gas streams are uniformly mixed in a coaxial mixing device and protected by an inert gas shield in the outer annular channel before finally entering the combustion reaction zone. This independent processing design allows for precise control of the catalyst and accelerator introduction rate, concentration, and physical state, fundamentally avoiding the agglomeration and inhomogeneity problems caused by single-injection methods. Compared to direct liquid-phase injection, gas-phase feeding eliminates the concentration gradient during droplet evaporation, fundamentally preventing catalyst particle nucleation and agglomeration.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, component splitting or combination, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-channel catalyst introduction system for the continuous preparation of carbon nanotubes by combustion, characterized in that, include: The catalyst gasification device includes a first injection pump, a carrier gas branch and a heated gasifier connected thereto, for fully vaporizing the metal-organic precursor solution through the heated gasifier and mixing it with the carrier gas to form a catalyst gas phase flow. The accelerator screening and vaporization device includes a second injection pump, an electro-spray atomizer, an impact classifier, and a secondary evaporation tube connected thereto. It is used to atomize the sulfur-containing accelerator solution into fine droplets through the electro-spray atomizer, remove large droplets with a particle size greater than the critical particle size through the impact classifier, and then heat and convert it into a quasi-gas phase flow through the secondary evaporation tube. A coaxial mixing device includes a coaxial sleeve structure consisting of an inner tube and an outer tube. The inlet end of the inner tube is connected to the outlet of the heating gasifier and the outlet of the secondary evaporation tube, respectively. A central channel is formed inside the inner tube for uniformly mixing the catalyst gas phase flow and the promoter quasi-gas phase flow. An outer annular channel is formed between the inner tube and the outer tube for introducing an inert gas to protect the flow. The gas path and control unit, including a mass flow meter and a PID control module, is used to independently control the introduction rate of the catalyst and the promoter, respectively.

2. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The injection rate of the first injection pump is 1 to 10 mL / min, and the temperature of the heating element vaporizer is 100 to 300°C.

3. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The injection rate of the second injection pump is 0.5 to 5 mL / min, and the frequency of the electro-spray atomizer is 0.5 to 5 MHz.

4. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The critical particle size for the impact classifier is 5 μm.

5. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The temperature of the secondary evaporation tube is 200°C.

6. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The carrier gas in the branch is nitrogen, with a flow rate of 0.3–3 L / min.

7. The dual-channel catalyst introduction system for the continuous combustion preparation of carbon nanotubes according to claim 1, characterized in that: The inert gas in the outer annular channel is argon, with a flow rate of 2–10 L / min.

8. A method for continuously preparing carbon nanotubes by combustion using the system described in any one of claims 1-7, characterized in that, Includes the following steps: (a) The metal-organic precursor solution is fed into the heated gasifier at a set rate through the first injection pump. After being fully vaporized at 100-300°C, it is mixed with the carrier gas to form a catalyst gas phase flow. (b) The sulfur-containing accelerator solution is fed into the electrospray atomizer at a set rate through the second injection pump and atomized into fine droplets. After the droplets are removed by the impact classifier to remove large droplets with a particle size greater than 5 μm, they enter the secondary evaporation tube and are converted into a quasi-gas phase flow at 200°C. (c) The catalyst gas phase flow obtained in step (a) and the promoter quasi-gas phase flow obtained in step (b) are respectively introduced into the central channel of the coaxial mixing device for uniform mixing, while an inert gas is introduced through the outer annular channel to carry out the flow. (d) The mixed gas phase flow enters the combustion reaction zone and carbon nanotubes are continuously synthesized under flame conditions.

9. The method for continuous preparation of carbon nanotubes by combustion according to claim 8, characterized in that, The organometallic precursor is ferrocene, the solvent is ethanol, and the solution concentration is 5–20 mg / mL; the sulfur-containing accelerator is thiophene, the solvent is ethanol, and the volume fraction is 0.1%–2%.

10. The method for continuous preparation of carbon nanotubes by combustion according to claim 8, characterized in that, The combustion reaction is carried out under low-pressure premixed flame conditions, with an oxygen flow rate of 1–5 L / min and a combustion chamber pressure of 50–60 kPa.

Images