Carbon nanotube reaction system with independent temperature control and internal gas self-circulation function

Abstract

This invention discloses a carbon nanotube reaction system with independent temperature control and internal gas self-circulation, relating to the field of nanomaterial preparation technology. The reaction system includes a floating bed reactor containing multiple variable-diameter reaction channels. Each segment of the variable-diameter reaction channel is connected to a temperature control system for providing a gradient or constant temperature field. A variable-diameter circulation pipe is connected to each of the variable-diameter reaction channels, with the smaller diameter end of the circulation pipe connected to the larger diameter end of each channel, and vice versa. A raw material gas inlet structure is also connected to each of the variable-diameter reaction channels. This allows for independent temperature control of each region within the variable-diameter reaction channels, enabling controllable growth of carbon nanotubes through precise temperature gradient control. The variable-diameter circulation pipe can autonomously optimize the flow field within the reactor, significantly improving the uniformity of product quality and achieving controllable adjustment of carbon nanotube structural parameters.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a carbon nanotube reaction system with independent temperature control and internal gas self-circulation function. Background Technology

[0002] In the field of carbon nanomaterial preparation, floating catalyst chemical vapor deposition (FCCVD) has attracted much attention due to its unique advantages in the continuous preparation of macroscopic carbon nanotube assemblies. This method directly introduces the catalyst precursor into the reaction system, completing the catalyst decomposition, activation, and carbon nanotube growth processes in the gas phase, thus enabling the continuous and large-scale production of carbon nanotubes. However, through in-depth analysis and research of existing technologies, it has been found that current FCCVD technology still faces many technical bottlenecks and challenges in achieving high-quality, high-efficiency, and low-cost industrial production.

[0003] First, regarding continuous product collection and system reliability, existing technologies often suffer from design complexity or susceptibility to interference. For example, patent document CN116534842A discloses a continuous preparation device and method for sponge-like single-walled carbon nanotubes. While this device innovatively proposes a mechanical push-pull rod system for continuous product transfer, the complex mechanical system it relies on, consisting of hook-shaped push-pull rods, rectangular push-pull rods, and gate valves, faces severe reliability and sealing challenges under long-term high-temperature environments. More importantly, this mechanical collection method can easily damage the three-dimensional network structure of the sponge-like product during the push-pull process, affecting the structural integrity and mechanical properties of the final product.

[0004] Patent document CN214456876U discloses an apparatus for preparing multi-walled carbon nanotube films. This apparatus promotes the outflow of carbon nanotubes from the high-temperature reaction zone by setting a special electric brush blowing device in the reaction chamber. However, the inhomogeneity of this carbon nanotube growth environment will affect the uniformity and consistency of product quality. In addition, the design of this apparatus is mainly for the preparation of carbon nanotube films with specific morphologies, lacking adaptability to products with different morphologies, thus limiting the expansion of its application range.

[0005] Secondly, existing technologies exhibit significant limitations in terms of production continuity and economic efficiency. For example, patent document CN104098079A discloses a method for preparing carbon nanotube films using quartz as a fixed substrate and growing carbon nanotube films via template-free chemical vapor deposition. While this method can yield high-quality carbon nanotube films, its reliance on a specific quartz substrate and the difficulty in achieving continuous product collection result in low production efficiency, failing to meet the demands of large-scale industrial production. Furthermore, the high cost of the quartz substrate and its susceptibility to damage during high-temperature reactions further increase production costs, hindering the industrial application prospects of this technology. This fixed-substrate-based preparation method is essentially still a batch or semi-continuous production process, significantly lagging behind true continuous and automated production.

[0006] Furthermore, existing technologies generally have significant shortcomings in process intensification and comprehensive resource utilization. Most FCCVD processes do not pay sufficient attention to reactant utilization and system energy consumption, and lack effective integrated solutions for the efficient and economical recovery and recycling of unreacted raw materials (such as hydrogen and olefins) and carrier gases. This leads to high raw material consumption, high operating costs, and additional environmental burdens. In particular, in the pursuit of high yields, the direct emission of large amounts of unreacted carbon sources and carrier gases not only wastes resources but may also pollute the environment. In addition, existing technologies have not conducted in-depth research on the optimization of flow, heat transfer, and mass transfer processes within the reactor, and lack precise control methods for the temperature and concentration fields within the reactor. This directly affects the quality and preparation efficiency of carbon nanotubes.

[0007] Finally, existing technologies still face significant challenges in product quality control and process stability. The structural parameters of carbon nanotubes (such as diameter, wall density, length, and defect density) have a decisive impact on their final performance, but existing FCCVD technologies often struggle to precisely control these parameters. Issues such as uneven flow within the reactor, temperature fluctuations, and uneven catalyst distribution can lead to batch-to-batch variations in carbon nanotube product quality, affecting product stability and reliability. Particularly during long-term continuous operation, catalyst deactivation and carbon buildup within the reactor can further impact process stability and product quality consistency.

[0008] In summary, existing carbon nanotube preparation technologies sacrifice system simplicity and reliability in pursuit of continuous production, or introduce interfering factors affecting quality uniformity and limiting product diversity when attempting to control product morphology, or face cost and scalability challenges due to reliance on specific substrates and discontinuous processes, or neglect the efficient utilization of raw materials and energy conservation and consumption reduction in the process. Therefore, there is an urgent need for a novel carbon nanotube reaction system that can balance reactor flow field stability, achieve truly continuous production, adapt to multiple product morphologies, and effectively reduce raw material consumption and operating costs. Summary of the Invention

[0009] Given the problem of inconsistent product quality in current carbon nanotube reaction systems, the purpose of this invention is to provide a carbon nanotube reaction system with independent temperature control and internal gas self-circulation. This reactor system can achieve high efficiency, continuity, and green production process while ensuring product quality, and it also has high raw material utilization and low energy consumption.

[0010] This invention is achieved through the following technical solution:

[0011] This invention provides a carbon nanotube reaction system with independent temperature control and internal gas self-circulation function, comprising a floating bed reactor containing multiple variable-diameter reaction channels, each of which is connected to a temperature control system for providing a gradient or constant temperature field; variable-diameter circulation pipes are connected to the multiple variable-diameter reaction channels, with the smaller diameter end of the circulation pipe connected to the larger diameter end of the multiple variable-diameter reaction channels, and the larger diameter end of the circulation pipe connected to the smaller diameter end of the multiple variable-diameter reaction channels; and a raw material gas inlet structure is connected to the multiple variable-diameter reaction channels.

[0012] A mechanical hot-pressing device can be connected to the carbon nanotube outlet of the multi-stage variable-diameter reaction channel, allowing the generated carbon nanotubes to directly enter the mechanical hot-pressing device. This device uses a combination of multi-stage heating and temperature control to densify the carbon nanotubes. After the carbon nanotube material enters the pressing chamber, it is first initially compacted by a pre-pressing device. Then, progressive pressure is applied during the main pressing stage to promote tight bonding between the carbon nanotube bundles. Finally, the product structure is stabilized through a holding pressure stage. The entire pressing process is carried out in a controllable temperature environment, and the pressing parameters are automatically adjusted by real-time monitoring of the product density to ensure that the final carbon nanotube product has ideal bulk density and structural integrity.

[0013] Furthermore, the multi-segment variable diameter reaction channel includes multiple independent heating zones.

[0014] Furthermore, the independent heating zones are designated as Zone 1, Zone 2, up to Zone N, where N≥2; the temperature control of the heating zones is within the range of 400℃~1200℃.

[0015] Furthermore, the ratio of the inner diameter of the smaller diameter end to the inner diameter of the larger diameter end of the variable diameter circulation pipe is 1:(1~15).

[0016] Furthermore, the feed gas inlet structure includes a hydrogen inlet pipe, an argon inlet pipe, a mixed olefin inlet pipe, and a catalyst precursor inlet pipe connected to the multi-section variable diameter reaction channel.

[0017] In this invention, the mixed olefins used are at least two of ethylene, propylene, and butene; and the catalyst precursor is any one of ferrocene, cobalt dicene, or iron carbonyl.

[0018] Furthermore, the mixed olefin inlet pipe and the catalyst precursor inlet pipe are connected to the main inlet pipe via a tee connector, and the main inlet pipe is then connected to multiple branch pipes via a multi-way connector. Each segment of the multi-section variable diameter reaction channel is connected to a branch pipe, and each branch pipe is connected to a control valve.

[0019] Furthermore, a heating structure is connected to the main intake pipe. This heating structure can be a molten salt heating system.

[0020] Furthermore, an exhaust pipe is connected to the multi-section variable diameter reaction channel, and the exhaust pipe is connected to a hydrogen recovery device.

[0021] Furthermore, the hydrogen recovery device includes an injector connected to the exhaust pipe, the injector being connected to a membrane separation unit, the membrane separation unit being connected to a pressure swing adsorption system, and the pressure swing adsorption system being connected to a hydrogen reuse pipeline connected to the feed gas inlet structure.

[0022] Furthermore, the ejector is connected to a power pipeline, and a power pump is connected to the power pipeline. This power pump is a compressor. One end of the ejector is connected to the compressor, and the other end is connected to the membrane separation unit.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) The carbon nanotube reaction system of the present invention can achieve independent temperature control for each region in the multi-segment variable diameter reaction channel, and achieve controllable growth of carbon nanotubes through precise temperature gradient control. The connected variable diameter circulation pipe can autonomously optimize the flow field in the reactor. The structure of independent temperature control for each segment and the variable diameter circulation pipe significantly improves the uniformity of product quality and realizes the controllable adjustment of carbon nanotube structural parameters. In addition, the connected variable diameter circulation pipe is connected in parallel with the multi-segment variable diameter reaction channel. When the pressure drop of the multi-segment variable diameter reaction channel is abnormal, the variable diameter circulation pipe can be turned on to ensure the continuous and stable operation of the reaction process. This synergistic structure of multi-segment variable diameter reaction channel and variable diameter circulation pipe not only realizes the adaptive adjustment of reaction intensity, but also effectively prevents catalyst deposition and bed blockage through flow channel optimization, significantly improving the operational flexibility and reliability of the reactor, and realizing high-quality, continuous and low-energy-consumption preparation of carbon nanotubes.

[0025] (2) The carbon nanotube reaction system of the present invention adopts a five-zone independent temperature control method, which can precisely control the temperature of each of the five zones. The first zone is controlled at 400℃~600℃ to achieve catalyst preheating and activation, and the second to Nth zones are controlled at 600℃~1200℃ to complete the nucleation and growth of carbon nanotubes. This segmented temperature control design ensures that each growth stage of carbon nanotubes is carried out at the optimal temperature, which significantly improves the uniformity of product quality and structural integrity.

[0026] (3) The carbon nanotube reaction system of the present invention can form a left-to-right circulation flow in the multi-section variable diameter reaction channel by connecting a variable diameter circulation pipe. This internal circulation design not only enhances the mass and heat transfer efficiency in the multi-section variable diameter reaction channel, but also prolongs the residence time of the catalyst and reactants in the optimal reaction zone, thereby increasing the uniformity of the carbon nanotube growth environment by more than 50%, increasing the catalyst utilization rate by more than 40%, reducing raw material consumption by more than 60%, and increasing productivity by more than 45%. Compared with the ordinary floating catalyst method, the operating cost is reduced by 35%~40%, realizing the unity of high quality, high efficiency and economy in the carbon nanotube preparation process.

[0027] (4) The hydrogen recovery device connected in this invention can separate unreacted gas by pressure swing adsorption and return it to the floating bed reactor for reuse, thereby improving the utilization rate of raw materials. By setting the reactor as a multi-stage variable diameter structure and connecting it with the hydrogen recovery device, the recycling of raw materials is realized, which significantly improves product quality and production efficiency. It has the advantages of high conversion rate and good product consistency, and provides a reliable technical approach for the green and efficient preparation of carbon nanotubes.

[0028] (5) The jet separator in this invention is the core power structure. It uses a high-pressure power gas source to generate a vacuum effect, providing stable gas flow power for the entire reaction system. The jet separator ensures that the reactants form a stable sulfidation state in the multi-stage variable diameter reaction channel by precisely controlling the gas flow rate and pressure parameters, while realizing the efficient recycling of unreacted gas. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to the present invention;

[0031] Figure 2 This is a schematic diagram of the variable diameter circulation pipe in this invention.

[0032] Figure label:

[0033] 01-Mixed olefins inlet pipe, 02-Main inlet pipe, 03-Heating structure, 04-Branch pipe, 05-Argon inlet pipe, 06-Hydrogen inlet pipe, 07-Control valve, 08-Variable diameter circulation pipe, 09-Multi-stage variable diameter reaction channel, 10-Exhaust pipe, 11-Power pump, 12-Ejector, 13-First-stage membrane separation unit, 14-Second-stage membrane separation unit, 15-Pressure swing adsorption system, 16-Hydrogen recovery pipeline, 17-Power pipeline, 18-Mechanical hot pressing shaping device, 19-Catalyst precursor inlet pipe, 20-Catalyst storage tank, 21-Mixed olefins storage tank, 22-Temperature control system. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0035] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0036] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those different embodiments or examples.

[0037] In this application, unless otherwise stated, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "middle," "vertical," "horizontal," "lateral," and "longitudinal," etc., generally refer to the directions shown in the drawings or describe the relative positional relationships of the components in a vertical, perpendicular, or gravitational direction. They are used only to describe the relative positional relationships between the components or constituent parts and do not specifically limit the specific installation orientation of each component or constituent part. "Inner" and "outer" generally refer to the interior or exterior of the cavity relative to the chamber or the radial interior or exterior relative to the center of a circle. The above directional terms are defined for ease of understanding of the present invention and therefore do not constitute a limitation on the scope of protection of the present invention.

[0038] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0039] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0040] Furthermore, the structures, proportions, sizes, etc., drawn in the accompanying drawings of this application are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modification to the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that this application can produce, should still fall within the scope of the technical content disclosed in this application.

[0041] Example

[0042] like Figures 1-2 As shown, this embodiment provides a carbon nanotube reaction system with independent temperature control and internal gas self-circulation function, including a floating bed reactor containing multiple variable diameter reaction channels 09. Each segment of the multiple variable diameter reaction channels 09 is connected to a temperature control system 22 for providing a gradient or constant temperature field. The temperature control system 22 is a molten salt heating system. A variable diameter circulation pipe 08 is connected to the multiple variable diameter reaction channels 09. The small diameter end of the variable diameter circulation pipe 08 is connected to the large diameter end of the multiple variable diameter reaction channels 09, and the large diameter end of the variable diameter circulation pipe 08 is connected to the small diameter end of the multiple variable diameter reaction channels 09. A raw material gas inlet structure is connected to the multiple variable diameter reaction channels 09.

[0043] Specifically, the multi-segment variable-diameter reaction channel 09 includes five independent heating zones. These five independent heating zones are zone 1, zone 2, zone 3, zone 4, and zone 5. The temperature control for zone 1 is 500℃~600℃, zone 2 is 600℃~700℃, zone 3 is 700℃~800℃, zone 4 is 750℃~850℃, and zone 5 is 700℃~750℃. This five-zone independent temperature control method allows for precise temperature regulation of each zone. Zone 1 is controlled at 500℃~600℃ for catalyst preheating and activation; zone 2 at 600℃~700℃ for carbon nanotube nucleation; zone 3 at 700℃~800℃ for bulk growth; zone 4 at 750℃~850℃ for structural refinement; and zone 5 at 700℃~750℃ for final shaping. This segmented temperature control design ensures that each stage of carbon nanotube growth occurs at the optimal temperature, significantly improving the uniformity of product quality and structural integrity.

[0044] Specifically, the ratio of the inner diameter of the small-diameter end to the inner diameter of the large-diameter end of the variable-diameter circulation pipe 08 is 1:(1.5~3). The variable-diameter circulation pipe 08 achieves self-circulating flow within the reactor through its special structure of a small diameter at the left end and a large diameter at the right end. Connecting the variable-diameter circulation pipe 08 allows some material to circulate from left to right within the multi-segment variable-diameter reaction channel 09 through pressure difference. This internal circulation design not only enhances the mass and heat transfer efficiency within the multi-segment variable-diameter reaction channel 09 but also extends the residence time of the catalyst and reactants in the optimal reaction zone. This results in a more than 50% increase in the uniformity of the carbon nanotube growth environment, a more than 40% increase in catalyst utilization, a more than 60% reduction in raw material consumption, and a more than 45% increase in productivity. Compared to the ordinary floating catalyst method, operating costs are reduced by 35%~40%, achieving a balance between high quality, high efficiency, and economy in the carbon nanotube preparation process.

[0045] Specifically, the feed gas inlet structure includes a hydrogen inlet pipe 06, an argon inlet pipe 05, a mixed olefin inlet pipe 01, and a catalyst precursor inlet pipe 19 connected to the multi-section variable diameter reaction channel 09. The hydrogen inlet pipe 06 and the argon inlet pipe 05 are connected to the left side of the multi-section variable diameter reaction channel 09, and are arranged parallel to each other. The mixed olefin inlet pipe 01 is connected to a mixed olefin storage tank 21, and the catalyst precursor inlet pipe 19 is connected to a catalyst storage tank 20.

[0046] Specifically, the mixed olefin inlet pipe 01 and the catalyst precursor inlet pipe 19 are connected to the main inlet pipe 02 via a three-way connector. The main inlet pipe 02 is then connected to multiple branch pipes 04 via a multi-way connector. Each section of the multi-section variable diameter reaction channel 09 is connected to a branch pipe 04, and each branch pipe 04 is connected to a control valve 07.

[0047] Specifically, a heating structure 03, which is a molten salt heating system, is connected to the intake manifold 02. By connecting the heating structure 03 to the intake manifold 02, the mixed olefins and catalyst precursors can be preheated before entering the multi-stage variable diameter reaction channel 09, thereby shortening the reaction time in the multi-stage variable diameter reaction channel 09 and improving production efficiency.

[0048] Specifically, an exhaust pipe 10 is connected to the multi-section variable-diameter reaction channel 09, and the exhaust pipe 10 is connected to a hydrogen recovery device. The hydrogen recovery device includes an injector 12 connected to the exhaust pipe 10, the injector 12 connected to a membrane separation unit, the membrane separation unit connected to a pressure swing adsorption system 15, and the pressure swing adsorption system 15 connected to a hydrogen recycling pipeline 16 connected to the feed gas inlet structure. The injector 12 is connected to a power pipeline 17, and a power pump 11 is connected to the power pipeline 17. This power pipeline 17 can be directly connected to the main intake pipe 02.

[0049] The membrane separation unit consists of a primary membrane separation unit 13 and a secondary membrane separation unit 14, forming a two-stage membrane separation structure. It can recover and purify more than 95% of the hydrogen in the reaction tail gas and return it to the reaction system for recycling.

[0050] By connecting a hydrogen recovery device, unreacted gases can be separated by pressure swing adsorption and returned to the floating bed reactor for reuse, thus improving the utilization rate of raw materials. By setting the reactor as a multi-stage variable diameter structure and connecting it to a hydrogen recovery device, the recycling of raw materials is realized, significantly improving product quality and production efficiency. It has the advantages of high conversion rate and good product consistency, providing a reliable technical approach for the green and efficient preparation of carbon nanotubes.

[0051] In other specific embodiments, a mechanical hot-pressing device 18 can be connected to the carbon nanotube outlet of the multi-segment variable-diameter reaction channel 09. This allows the generated carbon nanotubes to directly enter the mechanical hot-pressing device 18. This device can densify the carbon nanotubes through a combination of multi-stage heating and temperature control. After the carbon nanotube material enters the pressing chamber, it is first pre-compacted by a pre-pressing device. Then, progressive pressure is applied during the main pressing stage to promote tight bonding between the carbon nanotube bundles. Finally, the product structure is stabilized through a holding pressure stage. The entire pressing process is carried out in a controllable temperature environment. By automatically adjusting the pressing parameters through real-time monitoring of the product density, it is ensured that a carbon nanotube product with ideal bulk density and structural integrity is obtained.

[0052] Working principle: When the carbon nanotube reaction system is in use, the carbon source is introduced into the multi-section variable diameter reaction channel 09 through the mixed olefin inlet pipe 01, the catalyst is introduced into the multi-section variable diameter reaction channel 09 through the catalyst precursor inlet pipe 19, hydrogen is introduced into the multi-section variable diameter reaction channel 09 through the hydrogen inlet pipe 06, and argon is introduced into the multi-section variable diameter reaction channel 09 through the argon inlet pipe 05.

[0053] After the mixed olefins and catalyst precursors exit the storage tank, they split into two streams. One stream is pressurized by the power pump 11 (compressor) and enters the injector 12, while the other stream enters from the lower end of the multi-stage variable-diameter reaction channel 09. All materials entering the multi-stage variable-diameter reaction channel 09 flow from left to right within it. Five independent heating zones arranged axially in the multi-stage variable-diameter reaction channel 09 provide a gradient or constant temperature field. Under the action of the catalyst, the mixed olefins are cracked, and carbon nanotubes are grown by chemical vapor deposition on the floating catalyst. The connected variable-diameter circulation pipe 08, with its smaller diameter at the left end and larger diameter at the right end, can utilize the pressure difference to create a left-to-right circulating flow of some materials within the multi-stage variable-diameter reaction channel 09. Ultimately, at the right end of the multi-stage variable-diameter reaction channel 09, the carbon nanotubes aggregate to form macroscopic filamentous materials. During the reaction, residual gas is discharged into the injector 12 through the exhaust pipe 10, and then enters the primary membrane separation unit 13 and the secondary membrane separation unit 14 for separation and purification, achieving efficient hydrogen recovery. The hydrogen purified by the primary and secondary membrane separation units 13 and 14 further enters the pressure swing adsorption system 15 for further purification, improving the purity of the hydrogen and enabling its reuse. For example, the purified hydrogen can be reused through the hydrogen recycling pipe 16 into the multi-stage variable diameter reaction channel 09. Additionally, other gases separated from the membrane separation unit and the pressure swing adsorption system 15 can also be used as a power source to be introduced into the injector 12, or they can be reused again in the multi-stage variable diameter reaction channel 09.

[0054] The carbon nanotube reaction system of this invention enables independent temperature control of each region in the multi-segment variable-diameter reaction channel 09. Controllable growth of carbon nanotubes is achieved through precise temperature gradient control. The connected variable-diameter circulation pipe 08 can autonomously optimize the flow field within the reactor. The combined structure of independent temperature control for each segment and the variable-diameter circulation pipe 08 significantly improves the uniformity of product quality and achieves controllable adjustment of carbon nanotube structural parameters. Furthermore, the connected variable-diameter circulation pipe 08 is connected in parallel with the multi-segment variable-diameter reaction channel 09. When the pressure drop in the multi-segment variable-diameter reaction channel 09 is abnormal, the variable-diameter circulation pipe 08 can be activated to ensure continuous and stable operation of the reaction process. This synergistic structure of the multi-segment variable-diameter reaction channel 09 and the variable-diameter circulation pipe 08 not only achieves adaptive adjustment of reaction intensity but also effectively prevents catalyst deposition and bed blockage through flow channel optimization, significantly improving the reactor's operational flexibility and reliability, and realizing high-quality, continuous, and low-energy-consumption preparation of carbon nanotubes.

[0055] Compared to traditional carbon nanotube preparation systems, this carbon nanotube reaction system, featuring independent temperature control and internal gas self-circulation, achieves a comprehensive improvement in both the quality and efficiency of the preparation process through the synergistic effect of five-zone precise temperature control, internal circulation design, and a gas recovery system. Compared to traditional single-zone reactors, the five-zone temperature control system improves product quality uniformity by over 50%; the internal circulation design improves raw material utilization by over 40% compared to traditional direct-flow reactors; and the gas recovery system reduces raw material consumption by over 60% compared to traditional direct-discharge processes, achieving a balance between high quality, high efficiency, and cost-effectiveness in the carbon nanotube preparation process.

[0056] Experimental Example 1

[0057] This invention utilizes a carbon nanotube reaction system with independent temperature control and internal gas self-circulation to prepare few-walled carbon nanotubes. The reactor has an outer diameter of 200 mm and a reaction zone length of 1000 mm. The temperatures of the five zones are set at 550℃, 680℃, 800℃, 820℃, and 750℃, respectively. The variable-diameter tube has an inner diameter of 25 mm at the left end and 60 mm at the right end, and is made of quartz. The hydrogen flow rate is 200 ml / min, the argon flow rate is 300 ml / min, the ethylene to propylene molar ratio is 4:1, and the ferrocene catalyst concentration is 0.1 mol% of the carbon source molar amount in the feed gas. The feed pressure is 0.1 MPa. Under these conditions, continuous operation for 24 hours successfully produced black, glossy, and high-strength carbon nanotube filaments. The average diameter of the carbon nanotubes is approximately 8 nm. After hydrogen recovery and recycling, the total utilization rate is increased to over 95%, and the total olefin conversion rate is approximately 65%.

[0058] Compared to traditional carbon nanotube preparation devices, this carbon nanotube reaction system, featuring independent temperature control and internal gas self-circulation, achieves a comprehensive improvement in both the quality and efficiency of the preparation process through the synergistic effect of five-zone independent temperature control, internal circulation via a variable-diameter circulation tube, and a gas recovery system. Compared to traditional single-zone reactors, the five-zone temperature control system improves product quality uniformity by over 80%; the internal circulation design increases raw material utilization by over 40% compared to traditional reactors; and the gas recovery system reduces raw material consumption by over 60% compared to traditional direct-discharge processes.

[0059] Experimental Example 2

[0060] Double-walled carbon nanotubes were prepared using the carbon nanotube reaction system of this invention, which features independent temperature control and internal gas self-circulation. The reactor size was the same as in Example 1. Process parameters were adjusted: the temperatures in the five zones were set to 500℃, 600℃, 720℃, 780℃, and 700℃, respectively; pure ethylene was used as the carbon source; and the concentration of the cobalt-cerocene catalyst was increased to 0.15 mol%. Other conditions were the same as in Example 1. The resulting carbon nanotubes had finer diameters and better flexibility, and the product was mainly double-walled carbon nanotubes with an average diameter of 3 nm. Under these conditions, the carbon nanotube growth rate was increased by 20% compared to Example 1, and the product structure was more uniform.

[0061] Experimental Example 3

[0062] To assess the long-term stability of the system, it was operated continuously for 60 hours under the conditions of Example 1. Temperature fluctuations in each zone were less than ±5°C, and the ferrocene catalyst concentration was 0.1 mol% of the carbon source molarity in the feed gas. The feed pressure was 0.12 MPa, and the total utilization rate of hydrogen was increased to over 95% after recycling. The winding tension was stable, and the produced carbon nanotube filaments exhibited consistent properties. The quality indicators of the carbon nanotube products fluctuated within ±3%, demonstrating the system's ability to operate stably over the long term.

[0063] The carbon nanotube reaction system of this invention, which has independent temperature control and internal gas self-circulation function, has no application limitations. It can be used not only for the production of few-walled and double-walled carbon nanotubes, but also for the preparation of multi-walled carbon nanotubes and doped and modified carbon nanotube materials by adjusting the process parameters. The system has a wide range of raw material adaptability and can be used in various fields such as scientific research and industrial production.

[0064] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For those skilled in the art, it is obvious that this application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe various possible combinations separately. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this application is defined by the appended claims rather than the foregoing description, and therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included within this application.

Claims

1. A carbon nanotube reaction system with independent temperature control and internal gas self-circulation functions, characterized in that, The reactor includes a floating bed reactor containing multiple variable diameter reaction channels (09), each of which is connected to a temperature control system (22) for providing a gradient or constant temperature field; a variable diameter circulation pipe (08) is connected to the multiple variable diameter reaction channels (09), the small diameter end of the variable diameter circulation pipe (08) is connected to the large diameter end of the multiple variable diameter reaction channels (09), and the large diameter end of the variable diameter circulation pipe (08) is connected to the small diameter end of the multiple variable diameter reaction channels (09); the multiple variable diameter reaction channels (09) are connected to a raw material gas inlet structure.

2. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 1, characterized in that, The multi-segment variable diameter reaction channel (09) includes multiple independent heating zones.

3. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 2, characterized in that, The independent heating zones are designated as Zone 1, Zone 2, up to Zone N, where N ≥ 2, and the temperature control range of the multi-level independent heating zones is 400℃~1200℃.

4. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 1, characterized in that, The ratio of the inner diameter of the small diameter end to the inner diameter of the large diameter end of the variable diameter circulation pipe (08) is 1:(1~15).

5. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 1, characterized in that, The feed gas inlet structure includes a hydrogen inlet pipe (06), an argon inlet pipe (05), a mixed olefin inlet pipe (01), and a catalyst precursor inlet pipe (19) connected to the multi-section variable diameter reaction channel (09).

6. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 5, characterized in that, The mixed olefin inlet pipe (01) and the catalyst precursor inlet pipe (19) are connected to the main inlet pipe (02) via a three-way connector. The main inlet pipe (02) is then connected to multiple branch pipes (04) via a multi-way connector. Each section of the multi-section variable diameter reaction channel (09) is connected to a branch pipe (04), and each branch pipe (04) is connected to a control valve (07).

7. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 6, characterized in that, A heating structure (03) is connected to the intake manifold (02).

8. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 1, characterized in that, An exhaust pipe (10) is connected to the multi-section variable diameter reaction channel (09), and the exhaust pipe (10) is connected to a hydrogen recovery device.

9. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 8, characterized in that, The hydrogen recovery device includes an injector (12) connected to the exhaust pipe (10), the injector (12) connected to a membrane separation unit, the membrane separation unit connected to a pressure swing adsorption system (15), and the pressure swing adsorption system (15) connected to a hydrogen recycling pipeline (16) connected to the raw material gas inlet structure.

10. The carbon nanotube reaction system with independent temperature control and internal gas self-circulation function according to claim 8, characterized in that, The injector (12) is connected to a power pipe (17), and a power pump (11) is connected to the power pipe (17).

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