Carbon nanotubes and methods for making the same

Abstract

The application relates to the technical field of material synthesis, and provides a carbon nanotube and a preparation method thereof, the preparation method comprising the following steps: preparing a spinel crystal structure of FeCoMgO as a metal catalyst, the specific surface area of the metal catalyst being 220-300 cm 3 / g; introducing the metal catalyst and a carbon source into a carbon nanotube growth device, reacting under first reaction conditions to obtain a first reaction product; reacting the first reaction product under second reaction conditions to obtain a second reaction product; and crushing the second reaction product to obtain the carbon nanotube. Through the above scheme, the dispersibility of the carbon nanotube is improved, and the problem of uneven mixing of the carbon nanotube and a high polymer composite material in a short time is solved.

Description

Technical Field

[0001] This application belongs to the field of materials synthesis technology, and in particular relates to a carbon nanotube and its preparation method. Background Technology

[0002] Carbon nanotubes are one-dimensional quantum materials with a unique structure, widely used in the preparation of polymer materials. During the preparation process, carbon nanotubes and polymer composites need to be completely mixed within a short time. However, this shear mixing process generates a large amount of heat, resulting in a highly uneven melt temperature distribution within the composite material, leading to inhomogeneous mixing and consequently, non-uniform properties. Therefore, to improve the performance of composite materials, the problem of uneven mixing of carbon nanotubes and polymer composites within a short time remains to be solved. Summary of the Invention

[0003] The purpose of this application is to provide a carbon nanotube and its preparation method, which aims to solve the problem of uneven mixing of carbon nanotubes and polymer composite materials in a short time.

[0004] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0005] In a first aspect, this application provides a method for preparing carbon nanotubes, comprising:

[0006] A spinel-structured FeCoMgO catalyst was prepared as a metal catalyst, the specific surface area of ​​which was 220–300 cm². 3 / g;

[0007] The metal catalyst and carbon source are introduced into a carbon nanotube growth device and reacted under the first reaction conditions to obtain the first reactant.

[0008] The first reactant is reacted under the second reaction conditions to obtain the second reactant;

[0009] The second reactant was crushed to obtain carbon nanotubes.

[0010] Preferably, the preparation of the metal catalyst includes:

[0011] The metal salt and reaction aid are mixed and dissolved according to a preset molar ratio to obtain the first solution;

[0012] The first solution is mixed with an alkaline solution and emulsified to obtain an emulsion product;

[0013] The emulsion product was subjected to solid-liquid separation to obtain a precipitate;

[0014] The precipitate is calcined under preset conditions for a preset time to obtain the calcined product.

[0015] The calcined product is placed under preset reduction conditions to undergo a reduction reaction, thereby obtaining a metal catalyst.

[0016] Preferably, the metal salt includes ferric nitrate, cobalt nitrate, and / or magnesium nitrate, and the reaction aid includes ammonium molybdate. Correspondingly, the step of mixing and dissolving the metal salt and reaction aid in a preset molar ratio to obtain a first solution includes:

[0017] Ferric nitrate, cobalt nitrate, and / or magnesium nitrate are mixed and dissolved with ammonium molybdate in a predetermined molar ratio to obtain the first solution.

[0018] Preferably, the step of mixing and emulsifying the first solution with an alkaline solution to obtain an emulsion product includes:

[0019] The first solution and the alkaline solution are simultaneously dripped into the emulsification device through a transmission device, and the mixture is reacted for a first preset time to obtain a pre-product.

[0020] The pre-product is aged for a second preset time to obtain an emulsified product.

[0021] Preferably, the solid-liquid separation operation of the emulsion product to obtain a precipitate includes:

[0022] The emulsion product was centrifuged to separate the solid material.

[0023] The solid substance was dried to obtain a precipitate.

[0024] Preferably, the step of placing the calcined product under preset reduction conditions for a reduction reaction to obtain a metal catalyst includes:

[0025] The calcined product is placed in a reducing atmosphere and reacted at a preset reducing temperature for a preset reducing time to obtain a metal catalyst.

[0026] Preferably, the metal catalyst and the first carbon source atmosphere are introduced into the carbon nanotube growth device, and the reaction is carried out at a first reaction temperature for a first reaction time to obtain a first reactant; the first reactant and the second carbon source atmosphere are introduced into the carbon nanotube growth device, and the reaction is carried out at a second reaction temperature for a second reaction time to obtain a second reactant.

[0027] Preferably, during the first reaction, the mass ratio of the first carbon source atmosphere flow rate to the metal catalyst is 0.1–1 L / min: 0.1–0.5 g;

[0028] And / or, during the second reaction, the flow rate of the second carbon source atmosphere to the mass ratio of the metal catalyst is 0.6–1 L / min: 0.1–0.5 g.

[0029] Preferably, the first reaction temperature is 600–720°C, and the first reaction time is 5–23 min;

[0030] And / or, the second reaction temperature is 650–750°C, and the second reaction time is 17–27 min.

[0031] In a second aspect, this application provides a carbon nanotube, which is prepared using the method described in any of the first aspects above.

[0032] Beneficial effects of this application

[0033] This application provides a method for preparing carbon nanotubes, the method comprising: preparing a spinel crystal structure of FeCoMgO as a metal catalyst, the metal catalyst having a specific surface area of ​​220–300 cm². 3 / g; The metal catalyst and carbon source are introduced into a carbon nanotube growth device and reacted under the first reaction conditions to obtain the first reactant; the first reactant is then reacted under the second reaction conditions to obtain the second reactant; the second reactant is pulverized to obtain carbon nanotubes. The inventors of this application have discovered that improving the dispersibility of carbon nanotubes can solve the problem of uneven mixing of carbon nanotubes and polymer composites in a short time, and that there is a certain correlation between the crystal structure purity and specific surface area of ​​the metal catalyst and the dispersibility of carbon nanotubes. To improve the dispersibility of carbon nanotubes, this application prepares a spinel crystal structure of FeCoMgO as a metal catalyst. The purity of this crystal structure can control the defects of carbon nanotubes and improve the activity of individual catalyst particles; secondly, the specific surface area of ​​this catalyst can improve the uniformity and dispersibility of the active sites of the catalyst, making it less prone to agglomeration during the carbon nanotube growth stage. Furthermore, by modifying the carbon nanotube growth process, the growth of carbon nanotubes is first controlled in two stages to prevent premature catalyst deactivation during the reaction and ensure the uniformity of carbon nanotube growth. Secondly, the aspect ratio of the carbon nanotubes is controlled within a certain range, significantly reducing the degree of entanglement while maintaining the conductivity of the carbon nanotubes. This process allows for the exploration of the optimal aspect ratio for the mixing characteristics of carbon nanotubes in this application field. These measures achieve the goal of controlling the dispersion of carbon nanotubes, thereby preparing highly dispersed carbon nanotubes and solving the problem of uneven material mixing. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0035] Figure 1 This is one of the flowcharts of a method for preparing carbon nanotubes provided in the embodiments of this application;

[0036] Figure 2 This is a second flowchart of a method for preparing carbon nanotubes provided in the embodiments of this application;

[0037] Figure 3 This is the third flowchart of a method for preparing carbon nanotubes provided in the embodiments of this application;

[0038] Figure 4 This is the X-ray diffraction pattern of the metal catalyst provided in the embodiments of this application;

[0039] Figure 5 This is one of the scanning electron microscope images of carbon nanotubes provided in the embodiments of this application;

[0040] Figure 6 This is the second scanning electron microscope image of carbon nanotubes provided in the embodiments of this application;

[0041] Figure 7 This is a scanning electron microscope image of carbon nanotubes prepared according to the prior art, provided in the embodiments of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] For ease of description, the terms "first," "second," etc., used in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0044] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0045] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0046] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0047] Carbon nanotubes are one-dimensional quantum materials with a unique structure, widely used in the preparation of polymer materials, especially plastics such as ABS, PP, PS, PC, and PEEK. However, in existing material preparation processes, carbon nanotubes and polymer composites cannot be mixed uniformly in a short time, and the properties of the prepared materials also suffer from inhomogeneity. To address these issues, this application proposes a method for preparing carbon nanotubes.

[0048] Figure 1 One of the flowcharts for a method of preparing carbon nanotubes provided in an embodiment of this application is shown.

[0049] Reference Figure 1 The method for preparing carbon nanotubes provided in this application includes the following steps:

[0050] Step S100: Prepare a spinel crystal structure of FeCoMgO as a metal catalyst, wherein the specific surface area of ​​the metal catalyst is 220-300 cm². 3 / g;

[0051] Step S101: The metal catalyst and carbon source are introduced into the carbon nanotube growth device and reacted under the first reaction conditions to obtain the first reactant;

[0052] Step S102: The first reactant is placed under the second reaction conditions to react and obtain the second reactant;

[0053] Step S103: Crush the second reactant to obtain carbon nanotubes.

[0054] The inventors of this application discovered through research that there is a certain correlation between the crystal structure purity and specific surface area of ​​metal catalysts and the dispersion performance of carbon nanotubes. Improving the dispersibility of carbon nanotubes can solve the problem of uneven mixing of carbon nanotubes and polymer composites in a short time. Therefore, the inventors of this application improved the dispersibility of carbon nanotubes by controlling the crystal structure and specific surface area of ​​the metal catalyst to solve the problem of uneven material mixing. The crystal structure of the metal catalyst prepared by the above method is mainly a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm³. 3 / g.

[0055] It can be seen that, through Figure 1 The embodiments shown can improve the dispersibility of carbon nanotubes, thereby solving the problem of uneven mixing of carbon nanotubes and polymer composites, and at the same time providing a new means of regulating carbon nanotubes.

[0056] The following is about Figure 1 Step S100 will be described in detail. Figure 2 The second flowchart illustrates a method for preparing carbon nanotubes according to an embodiment of this application. This process is... Figure 1 The specific steps of step S100 are detailed below. Refer to... Figure 2 Step S100 specifically includes the following steps:

[0057] Step S200: Mix and dissolve the metal salt and reaction aid according to a preset molar ratio to obtain the first solution;

[0058] Step S201: Mix and emulsify the first solution with an alkaline solution to obtain an emulsion product;

[0059] Step S202: Perform solid-liquid separation on the emulsion product to obtain a precipitate;

[0060] Step S203: Place the precipitate under preset conditions and calcine for a preset time to obtain the calcined product;

[0061] Step S204: Place the calcined product under preset reduction conditions to carry out a reduction reaction to obtain a metal catalyst.

[0062] Among them, metal salts are salts containing metal ions, and can be iron salts, cobalt salts and / or magnesium salts. Iron salts can be ferric nitrate, ferric chloride or ferric sulfate, etc., cobalt salts can be cobalt nitrate, etc., and magnesium salts can be magnesium nitrate, magnesium chloride or magnesium sulfate, etc.

[0063] Among them, the reaction aid can maintain the reaction activity of the main catalyst during the carbon nanotube production process, and can be ammonium molybdate, ammonium metavanadate or calcium nitrate.

[0064] The preset molar ratio of iron salt, cobalt salt, molybdenum salt, and magnesium salt is (5-9):1:0.05:(20-100). For example, ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate are mixed and dissolved in a molar ratio of (5-9):1:0.05:(20-100). This molar ratio setting results in a high carrier content, facilitates the formation of sheet-like carriers by the magnesium system, and provides numerous active sites with good dispersibility.

[0065] For example, ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate are mixed and dissolved in a molar ratio of 9:1:0.05:20 to obtain a first solution. This first solution is then emulsified with an alkaline solution to obtain an emulsion product. The emulsion product is subjected to solid-liquid separation to obtain a precipitate. The precipitate is calcined under preset conditions for a preset time to obtain a calcined product. This calcined product is then subjected to a reduction reaction under preset reduction conditions to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g.

[0066] For example, ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate are mixed and dissolved in a molar ratio of 7:1:0.05:50 to obtain a first solution. This first solution is then emulsified with an alkaline solution to obtain an emulsion product. The emulsion product is subjected to solid-liquid separation to obtain a precipitate. The precipitate is calcined under preset conditions for a preset time to obtain a calcined product. This calcined product is then subjected to a reduction reaction under preset reduction conditions to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g.

[0067] For example, ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate are mixed and dissolved in a molar ratio of 6:1:0.05:60 to obtain a first solution. This first solution is then emulsified with an alkaline solution to obtain an emulsion product. The emulsion product is subjected to solid-liquid separation to obtain a precipitate. The precipitate is calcined under preset conditions for a preset time to obtain a calcined product. This calcined product is then subjected to a reduction reaction under preset reduction conditions to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g.

[0068] By controlling the catalyst formulation and preparation process as described above, the whisker structure and specific surface area of ​​the catalyst can be controlled. The main crystal form of the metal catalyst prepared according to the above method is the spinel structure of FeCoMgO, and it has a high specific surface area, that is, it has high dispersibility.

[0069] The following is about Figure 2 Step S201 will be explained in detail. Figure 3 This is a third flowchart illustrating a method for preparing carbon nanotubes according to an embodiment of this application. This flowchart details the steps of step S201. (Refer to...) Figure 3 Step S201 specifically includes the following steps:

[0070] Step S300: The first solution and the alkaline solution are simultaneously dripped into the emulsification device through a transmission device, and the mixture is reacted for a first preset time to obtain the pre-product;

[0071] Step S301: Aging the pre-product for a second preset time to obtain the emulsified product.

[0072] The alkaline solution can be prepared using ammonia, sodium carbonate, or sodium bicarbonate, or a mixture of these reagents. The pH of the alkaline solution is 8–10, and can specifically be 8, 8.5, 9, 9.5, or 10.

[0073] The first preset duration is 2 to 6 hours, and the specific values ​​can include: 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0074] The second preset duration is 2 to 4 hours, and the specific values ​​can include 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0075] Among them, the transmission equipment can be a peristaltic pump, injection pump or diaphragm pump, etc., and the emulsification equipment can be an emulsification homogenizer, vacuum homogenizing emulsifier or high shear emulsifier, etc.

[0076] For example, an alkaline solution is prepared using ammonia water, and the alkaline solution and the first solution are simultaneously dripped into an emulsifier using a peristaltic pump. The mixture is stirred and reacted for 4 hours to obtain a pre-product. The pre-product is then aged for 3 hours to obtain an emulsified product.

[0077] For example, an alkaline solution is prepared using sodium carbonate. This alkaline solution and the first solution are simultaneously dripped into an emulsifier using a peristaltic pump. The mixture is stirred and reacted for 3 hours to obtain a pre-product. The pre-product is then aged for 2.5 hours to obtain an emulsified product.

[0078] For example, an alkaline solution is prepared using sodium carbonate and ammonia. This alkaline solution and the first solution are simultaneously dripped into an emulsifier using a peristaltic pump and stirred and mixed for 3 hours to obtain a pre-product. The pre-product is then aged for 4 hours to obtain an emulsified product.

[0079] The above method ensures that the solution is thoroughly mixed and reacts completely.

[0080] The following is a detailed description of step S202. In step S202, regarding the solid-liquid separation operation of the emulsion product to obtain a precipitate, the solid-liquid separation operation may be as follows: after removing the solid substances from the emulsion product, the precipitate is obtained by static drying, baking, vacuum drying, or freeze drying.

[0081] Therefore, step S202 may specifically include: washing and centrifuging the emulsified product in a centrifuge to separate the solid substance, and then placing the solid substance in a vacuum drying oven and drying it at 190°C for 2–10 hours to obtain a precipitate. This method allows for the preparation of a dried precipitate for subsequent reactions.

[0082] Step S203 will now be described in detail. In embodiments achievable under this application, Figure 2 Step S203 includes: placing the precipitate under preset conditions and calcining it for a preset time to obtain the calcined product.

[0083] The preset calcination time is 3 to 6 hours, and the specific values ​​can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0084] The calcination temperature is 350 to 600℃, and specific values ​​can include 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃.

[0085] The calcination equipment can be a muffle furnace, a tube furnace, or a sintering furnace, etc.

[0086] For example, the precipitate is placed in a muffle furnace and calcined at 400°C for 5 hours to obtain the calcined product.

[0087] For example, the precipitate is placed in a tube furnace and calcined at 500°C for 4 hours to obtain the calcined product.

[0088] For example, the precipitate is placed in a tube furnace and calcined at 550°C for 3.5 hours to obtain the calcined product.

[0089] It should be noted that the specific values ​​mentioned above are examples, and other values ​​within the corresponding ranges are also included, which will not be elaborated upon in this application.

[0090] Step S204 will be described in detail below. In embodiments achievable in this application, Figure 2 Step S204 includes: placing the calcined product under preset reduction conditions to carry out a reduction reaction to obtain a metal catalyst.

[0091] The equipment used for the reduction reaction is a catalyst reduction and activation device.

[0092] The preset reduction conditions include: a reduction temperature of 620℃, a reduction reaction time of 30–50 min, a reduction atmosphere of nitrogen and hydrogen, a nitrogen to hydrogen ratio of (2–5):1, and a hydrogen flow rate to catalyst mass ratio of 0.1–0.5 L / min:0.1–0.5 g. These hydrogen content and flow rate settings were obtained by the inventors through extensive experimental adjustments, resulting in good catalyst reduction performance and reduced catalyst agglomeration during the reduction process.

[0093] The main crystal form of the prepared metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g, its X-ray diffraction pattern can be referenced. Figure 4 .

[0094] For example, the calcined product is added to a catalyst reduction and activation apparatus, the reduction temperature is set to 620°C, and a reducing atmosphere of nitrogen and hydrogen is introduced, with a nitrogen to hydrogen ratio of 3:1 and a hydrogen flow rate to catalyst mass ratio of 0.3 L / min: 0.2 g. The reaction is carried out under these conditions for 35 min to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g.

[0095] For example, the calcined product is added to a catalyst reduction and activation apparatus, the reduction temperature is set to 620°C, and a reducing atmosphere of nitrogen and hydrogen is introduced, with a nitrogen to hydrogen ratio of 4:1 and a hydrogen flow rate to catalyst mass ratio of 0.5 L / min: 0.3 g. The reaction is carried out under these conditions for 45 min to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g

[0096] For example, the calcined product is added to a catalyst reduction and activation apparatus, the reduction temperature is set to 620°C, and a reducing atmosphere of nitrogen and hydrogen is introduced, with a nitrogen to hydrogen ratio of 2:1 and a hydrogen flow rate to catalyst mass ratio of 0.1 L / min: 0.5 g. The reaction is carried out under these conditions for 50 min to obtain a metal catalyst. The main crystal form of this metal catalyst is a spinel structure of FeCoMgO, with a specific surface area of ​​220–300 cm². 3 / g.

[0097] Through the above reduction reaction, the calcined product can be restored to its catalytic activity, so as to obtain a metal catalyst with normal catalytic function.

[0098] The following is about Figure 1 The steps S101 to S103 are explained in detail.

[0099] Step S101 specifically includes the following steps:

[0100] A metal catalyst and a first carbon source atmosphere are introduced into a carbon nanotube growth device, and the reaction is carried out at a first reaction temperature for a first reaction time to obtain a first reactant.

[0101] Step S102 specifically includes the following steps:

[0102] The first reactant and the second carbon source atmosphere are introduced into the carbon nanotube growth device, and the reaction is carried out at the second reaction temperature for the second reaction time to obtain the second reactant.

[0103] It should be noted that the first carbon source atmosphere and the second carbon source atmosphere in this invention can be the same or different. Specifically, olefins, alkanes, and alkynes can be selected. Methane, ethylene, propylene, acetylene, etc. are preferred.

[0104] In this reaction, the first carbon source atmosphere can be alkyne, and the mass ratio of the first carbon source atmosphere flow rate to the metal catalyst is 0.1–1 L / min: 0.1–0.5 g. The first reaction stage, the catalyst induction stage, has lower catalyst activity and is suitable for a mild reaction. Therefore, the reaction temperature and reaction time can be appropriately lowered compared to the second reaction stage, and the carbon source flow rate can also be adjusted accordingly.

[0105] In this reaction, the second carbon source atmosphere can be alkane, and the flow rate of the second carbon source atmosphere to the mass ratio of the metal catalyst is 0.6–1 L / min: 0.1–0.5 g. During the second reaction stage, carbon decomposes and encapsulates a large amount of catalyst particles. A high proportion of carbon source atmosphere easily leads to catalyst deactivation, while a low proportion reduces production capacity. The above-mentioned ratio range ensures catalyst activity without affecting the production capacity of carbon nanotubes.

[0106] The first reaction temperature is 600-720℃, and specific values ​​can include: 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃ or 720℃.

[0107] The duration of the first reaction is 5 to 23 minutes, and the specific values ​​can include 5 minutes, 10 minutes, 15 minutes, 20 minutes or 23 minutes.

[0108] The second reaction temperature is 650–750℃, and specific values ​​may include: 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, or 750℃.

[0109] The duration of the second reaction is 17 to 27 minutes, and the specific values ​​can be 17 minutes, 20 minutes, 25 minutes or 27 minutes.

[0110] For example, a metal catalyst is fed into a carbon nanotube growth apparatus, propylene is introduced, the reaction temperature is set to 610°C, and the mass ratio of propylene flow rate to metal catalyst is 0.8 L / min:0.2 g. After reacting for 13 min, a first reactant is obtained. This first reactant is then placed in the carbon nanotube growth apparatus, propylene is introduced, the reaction temperature is set to 680°C, and the mass ratio of propylene flow rate to metal catalyst is 0.7 L / min:0.2 g. After reacting for 20 min, a second reactant is obtained. This second reactant is then conveyed to an air jet mill, and the powder particle size is controlled to be below 60 μm to obtain carbon nanotubes. Air jet milling of carbon nanotubes to control the powder particle size to below 60 μm can improve the dispersion performance of carbon nanotubes in resin.

[0111] For example, a metal catalyst is fed into a carbon nanotube growth device, propylene is introduced, the reaction temperature is set to 660°C, and the mass ratio of propylene flow rate to metal catalyst is 0.8 L / min: 0.4 g. After reacting for 20 min, a first reactant is obtained. The first reactant is then placed in the carbon nanotube growth device, propylene is introduced, the reaction temperature is set to 670°C, and the mass ratio of propylene flow rate to metal catalyst is 0.8 L / min: 0.4 g. After reacting for 18 min, a second reactant is obtained. The second reactant is then transported to an air jet mill, and the powder particle size is controlled to be below 60 μm to obtain carbon nanotubes.

[0112] For example, a metal catalyst is fed into a carbon nanotube growth device, propylene is introduced, the reaction temperature is set to 700°C, and the mass ratio of propylene flow rate to metal catalyst is 0.9 L / min: 0.5 g. After reacting for 10 min, a first reactant is obtained. The first reactant is placed in the carbon nanotube growth device, propylene is introduced, the reaction temperature is set to 710°C, and the mass ratio of propylene flow rate to metal catalyst is 0.6 L / min: 0.4 g. After reacting for 25 min, a second reactant is obtained. The second reactant is then transported to an air jet mill, and the powder particle size is controlled to be below 60 μm to obtain carbon nanotubes.

[0113] In the above embodiments of this application, by changing the growth process of carbon nanotubes, the growth of carbon nanotubes is divided into two stages for control, so that the catalyst is not easily deactivated prematurely during the reaction process, while ensuring the uniformity of carbon nanotubes during the growth process; in addition, the aspect ratio of carbon nanotubes is controlled within a certain range, so that the degree of carbon nanotube entanglement is greatly reduced, and in order to take into account the conductivity of carbon nanotubes, the optimal aspect ratio of carbon nanotubes with mixed characteristics in this application field is obtained through research. Figure 5 as well as Figure 6 The image shows a scanning electron microscope (SEM) image of carbon nanotubes prepared according to an embodiment of the present invention. The carbon nanotubes have a diameter of 7–20 nm, an aspect ratio of 5000–15000, and a specific surface area of ​​220–270 m².3 / g, D / G = 0.7~1.5, powder resistivity 20~70mΩ*cm (4MPa). The larger the aspect ratio, the better the conductivity of carbon nanotubes, but it will also cause the carbon nanotubes to become entangled. However, in this invention, carbon nanotubes with a high aspect ratio but less entanglement are obtained. Figure 7 Scanning electron microscope (SEM) images of carbon nanotubes prepared according to existing techniques are shown. Comparison of the SEM images reveals that the carbon nanotubes of this invention mostly extend in one direction, while the carbon nanotubes prepared according to existing techniques exhibit severe entanglement and generally present a mesh-like structure. Therefore, the carbon nanotubes prepared by this invention have better dispersion properties than ordinary carbon nanotubes, which can be inferred from their structure itself. Compared to ordinary carbon nanotubes, the carbon nanotubes of this invention can be quickly and uniformly mixed with polymer materials, making them suitable for polymer material molding and preparation processes.

[0114] The following description is based on specific embodiments.

[0115] Example 1

[0116] Ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate were mixed and dissolved in a molar ratio of 9:1:0.05:20 to obtain a first solution. An alkaline solution was prepared using ammonia water. This alkaline solution and the first solution were simultaneously added dropwise to an emulsifier using a peristaltic pump and stirred for 4 hours to obtain a preproduct. The preproduct was aged for 3 hours to obtain an emulsion. The emulsion was washed and centrifuged in a centrifuge to separate the solid material. The solid material was then placed in a vacuum drying oven and dried at 190°C for 8 hours to obtain a precipitate. The precipitate was placed in a tube furnace and calcined at 500°C for 4 hours to obtain a calcined product. The calcined product was added to a catalyst reduction and activation device, and the reduction temperature was set to 620°C. A reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen ratio of 3:1 and a hydrogen flow rate to catalyst mass ratio of 0.3 L / min:0.2 g. The reaction was carried out under these conditions for 35 minutes to obtain a metal catalyst.

[0117] A metal catalyst was fed into a carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 610℃, and the mass ratio of propylene flow rate to metal catalyst was 0.9 L / min: 0.4 g. After reacting for 13 min, a first reactant was obtained. This first reactant was then placed in the carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 680℃, and the mass ratio of propylene flow rate to metal catalyst was 0.8 L / min: 0.3 g. After reacting for 20 min, a second reactant was obtained. This second reactant was then transported to an air jet mill, and the particle size was controlled to be below 60 μm to obtain carbon nanotubes.

[0118] Example 2

[0119] Ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate were mixed and dissolved in a molar ratio of 6:1:0.05:60 to obtain a first solution. An alkaline solution was prepared using ammonia water. This alkaline solution and the first solution were simultaneously added dropwise to an emulsifier using a peristaltic pump and stirred for 3 hours to obtain a preproduct. The preproduct was then aged for 3 hours to obtain an emulsion. The emulsion was washed and centrifuged in a centrifuge to separate the solid material. The solid material was then placed in a vacuum drying oven and dried at 190°C for 5 hours to obtain a precipitate. The precipitate was placed in a tube furnace and calcined at 525°C for 4.5 hours to obtain a calcined product. The calcined product was added to a catalyst reduction and activation device, and the reduction temperature was set to 620°C. A reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen ratio of 2:1 and a hydrogen flow rate to catalyst mass ratio of 0.5 L / min:0.2 g. The reaction was carried out under these conditions for 45 minutes to obtain a metal catalyst.

[0120] A metal catalyst was fed into a carbon nanotube growth apparatus, propylene was introduced, the reaction temperature was set to 610℃, and the mass ratio of propylene flow rate to metal catalyst was 0.3 L / min: 0.2 g. After reacting for 17 min, a first reactant was obtained. The first reactant was then placed in the carbon nanotube growth apparatus, propylene was introduced, the reaction temperature was set to 740℃, and the mass ratio of propylene flow rate to metal catalyst was 0.7 L / min: 0.2 g. After reacting for 18 min, a second reactant was obtained. The second reactant was then transported to an air jet mill, and the particle size was controlled to be below 60 μm to obtain carbon nanotubes.

[0121] Example 3

[0122] Ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate were mixed and dissolved in a molar ratio of 8:1:0.05:70 to obtain a first solution. An alkaline solution was prepared using ammonia water. This alkaline solution and the first solution were simultaneously added dropwise to an emulsifier using a peristaltic pump and stirred for 5 hours to obtain a preproduct. The preproduct was aged for 3 hours to obtain an emulsion. The emulsion was washed and centrifuged in a centrifuge to separate the solid material. The solid material was then placed in a vacuum drying oven and dried at 190°C for 6 hours to obtain a precipitate. The precipitate was placed in a tube furnace and calcined at 550°C for 5.5 hours to obtain a calcined product. The calcined product was added to a catalyst reduction and activation device, and the reduction temperature was set to 620°C. A reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen ratio of 4:1 and a hydrogen flow rate to catalyst mass ratio of 0.4 L / min:0.2 g. The reaction was carried out under these conditions for 40 minutes to obtain a metal catalyst.

[0123] A metal catalyst was fed into a carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 610℃, and the mass ratio of propylene flow rate to metal catalyst was 0.6 L / min: 0.4 g. After reacting for 20 min, a first reactant was obtained. This first reactant was then placed in the carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 690℃, and the mass ratio of propylene flow rate to metal catalyst was 0.9 L / min: 0.2 g. After reacting for 27 min, a second reactant was obtained. This second reactant was then fed into an air jet mill, and the particle size was controlled to be below 60 μm to obtain carbon nanotubes.

[0124] Example 4

[0125] Ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate were mixed and dissolved in a molar ratio of 5:1:0.05:90 to obtain a first solution. An alkaline solution was prepared using ammonia water. This alkaline solution and the first solution were simultaneously added dropwise to an emulsifier using a peristaltic pump and stirred for 6 hours to obtain a preproduct. The preproduct was aged for 3 hours to obtain an emulsion. The emulsion was washed and centrifuged in a centrifuge to separate the solid material. The solid material was then placed in a vacuum drying oven and dried at 190°C for 5 hours to obtain a precipitate. The precipitate was placed in a tube furnace and calcined at 450°C for 5 hours to obtain a calcined product. The calcined product was added to a catalyst reduction and activation device, and the reduction temperature was set to 620°C. A reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen ratio of 5:1 and a hydrogen flow rate to catalyst mass ratio of 0.3 L / min:0.4 g. The reaction was carried out under these conditions for 50 minutes to obtain a metal catalyst.

[0126] A metal catalyst was fed into a carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 610℃, and the mass ratio of propylene flow rate to metal catalyst was 0.5 L / min: 0.3 g. After reacting for 23 min, a first reactant was obtained. This first reactant was then placed in the carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 720℃, and the mass ratio of propylene flow rate to metal catalyst was 0.7 L / min: 0.4 g. After reacting for 23 min, a second reactant was obtained. This second reactant was then transported to an air jet mill, and the particle size was controlled to be below 60 μm to obtain carbon nanotubes.

[0127] Example 5

[0128] Ferric nitrate, cobalt nitrate, ammonium molybdate, and magnesium nitrate were mixed and dissolved in a molar ratio of 8:1:0.05:40 to obtain a first solution. An alkaline solution was prepared using ammonia water. This alkaline solution and the first solution were simultaneously added dropwise to an emulsifier using a peristaltic pump and stirred for 3 hours to obtain a preproduct. The preproduct was then aged for 3 hours to obtain an emulsion. The emulsion was washed and centrifuged in a centrifuge to separate the solid material. The solid material was then placed in a vacuum drying oven and dried at 190°C for 7 hours to obtain a precipitate. The precipitate was placed in a tube furnace and calcined at 600°C for 3 hours to obtain a calcined product. The calcined product was added to a catalyst reduction and activation device, and the reduction temperature was set to 620°C. A reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen ratio of 3:1 and a hydrogen flow rate to catalyst mass ratio of 0.4 L / min:0.3 g. The reaction was carried out under these conditions for 40 minutes to obtain a metal catalyst.

[0129] A metal catalyst was fed into a carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 610℃, and the mass ratio of propylene flow rate to metal catalyst was 0.7 L / min: 0.3 g. After reacting for 15 min, a first reactant was obtained. This first reactant was then placed in the carbon nanotube growth apparatus, and propylene was introduced. The reaction temperature was set to 730℃, and the mass ratio of propylene flow rate to metal catalyst was 0.8 L / min: 0.3 g. After reacting for 25 min, a second reactant was obtained. This second reactant was then transported to an air jet mill, and the particle size was controlled to be below 60 μm to obtain carbon nanotubes.

[0130] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing carbon nanotubes, characterized by, The application relates to a preparation method of carbon nanotubes. A spinel crystal structure of FeCoMgO is prepared as a metal catalyst, and the specific surface area of the metal catalyst is 220-300 cm 3 / g. The metal catalyst and a carbon source are introduced into a carbon nanotube growth device to react under first reaction conditions, so as to obtain a first reaction product; The first reaction product and a second carbon source atmosphere are introduced into the carbon nanotube growth device to react under a second reaction temperature for a second reaction time, so as to obtain a second reaction product; The second reaction product is crushed to obtain the carbon nanotubes.

2. The method of claim 1, wherein the carbon nanotube is prepared by a method comprising the steps of: The metal catalyst is prepared by the following steps: ​ A metal salt and a reaction aid are mixed and dissolved according to a preset molar ratio to obtain a first solution; The first solution is mixed with an alkaline solution to obtain an emulsification product; The emulsification product is subjected to a solid-liquid separation operation to obtain a precipitate; The precipitate is calcined under a preset condition for a preset time to obtain a calcined product; The calcined product is subjected to a reduction reaction under a preset reduction condition to obtain the metal catalyst.

3. The method for preparing carbon nanotubes according to claim 2, characterized in that, The metal salt comprises iron nitrate, cobalt nitrate and / or magnesium nitrate, the reaction aid comprises ammonium molybdate, and correspondingly, the step of mixing and dissolving the metal salt and the reaction aid according to the preset molar ratio to obtain the first solution comprises: The iron nitrate, the cobalt nitrate and / or the magnesium nitrate and the ammonium molybdate are mixed and dissolved according to the preset molar ratio to obtain the first solution.

4. The method for preparing carbon nanotubes according to claim 2, characterized in that, The step of mixing and emulsifying the first solution with the alkaline solution to obtain the emulsification product comprises: The first solution and the alkaline solution are simultaneously dropped into an emulsification device through a conveying device, mixed and reacted for a first preset time to obtain a preliminary product; The preliminary product is aged for a second preset time to obtain the emulsification product.

5. The method for preparing carbon nanotubes according to claim 2, characterized in that, The step of subjecting the emulsification product to the solid-liquid separation operation to obtain the precipitate comprises: The emulsification product is subjected to a centrifugal operation to separate out solid substances; The solid substances are dried to obtain the precipitate.

6. The method of claim 2, wherein the carbon nanotubes are prepared by a method comprising the steps of: The step of subjecting the calcined product to the reduction reaction under the preset reduction condition to obtain the metal catalyst comprises: ​ The calcined product is placed in a reduction atmosphere and reacted under a preset reduction temperature for a preset reduction time to obtain the metal catalyst.

7. The method for preparing carbon nanotubes according to claim 1, characterized in that, The metal catalyst and a first carbon source atmosphere are introduced into a carbon nanotube growth device to react under a first reaction temperature for a first reaction time, so as to obtain a first reaction product.

8. The method of claim 7, wherein the carbon nanotubes are prepared by a method comprising the steps of: The mass ratio of the first carbon source atmosphere flow to the metal catalyst is 0.1-1 L / min: 0.1-0.5 g during the first reaction time; ​ And / or, the mass ratio of a second carbon source atmosphere flow to the metal catalyst is 0.6-1 L / min: 0.1-0.5 g during the second reaction time.

9. The method of claim 7 or 8, wherein the carbon nanotubes are prepared by a method comprising the steps of: The first reaction temperature is 600-720 DEG C, and the first reaction time is 5-23 min; ​ And / or, the second reaction temperature is 650-750 DEG C, and the second reaction time is 17-27 min.

10. A carbon nanotube, characterized by, The carbon nanotubes are prepared by the method according to any one of claims 1-9.

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