Nanocarbon catalyst for carbon nanotubes, preparation method and preparation method of carbon nanotubes

Abstract

The invention relates to the technical field of carbon materials, in particular to a nanocarbon catalyst for a carbon nanotube, a preparation method and a preparation method of the carbon nanotube, and the preparation method comprises the following steps: providing a carbon source, a heteroatom source, a metal salt with a catalytic active component and an inert material lining; dissolving a carbon source, a heteroatom source and a metal salt in a solvent to form a reaction solution; the reaction liquid is transferred into an inert material lining, a heating reaction is conducted for a period of time, a product is collected after cooling is conducted, the nano metal / carbon catalyst powder is obtained, the nano metal / carbon catalyst powder is of a C-X-Me structure, C represents a carbon element, X represents a heteroatom element, Me represents a metal element, and the C-X-Me structure is formed by chelating C-X sites and metal nanoparticles. The catalyst activity can be remarkably improved, and the high-temperature aggregation and sintering phenomena of the catalyst can be inhibited.

Description

Technical Field

[0001] The present application relates to the technical field of carbon materials, and in particular to a nano-carbon catalyst for carbon nanotubes, a preparation method and a preparation method of carbon nanotubes. Background Art

[0002] Carbon nanotubes are mainly seamless tubular structures composed of single-layer or multi-layer graphene sheets curled around the center at a certain spiral angle. According to the number of graphene layers, they can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. They have excellent conductive properties and can be used as a new conductive agent in new energy batteries and other fields.

[0003] The aspect ratio and carbon purity of carbon nanotubes are two core indicators that affect their conductivity, which directly determine the product performance of carbon nanotubes. In theory, the thinner the diameter of carbon nanotubes, the longer the length, the higher the heat exchange performance along the length direction, and the higher the carbon purity, the better the conductivity; and compared with multi-walled carbon nanotubes, oligo-walled carbon nanotubes have stronger conductivity, less addition, and better safety. The best strategy for obtaining low-diameter carbon nanotubes at present is to prepare catalysts with stable metal nanoparticles of predefined size and prevent them from aggregating and becoming thicker during the preparation process of chemical vapor deposition (CVD). Therefore, in order to control the diameter and wall number of carbon nanotubes, the aggregation and sintering of metal nanoparticles under high temperature conditions are generally alleviated by reducing the loading amount of active metals. However, the reduction of metal loading will correspondingly reduce the active sites involved in the growth of carbon nanotubes, resulting in a reduction in the number of carbon nanotubes obtained and a decrease in carbon yield. Summary of the invention

[0004] In view of the above problems in the prior art, the present application provides a nanocarbon catalyst for carbon nanotubes, a preparation method and a preparation method of carbon nanotubes. The specific technical solutions are as follows:

[0005] In one aspect, the present application provides a method for preparing a nanocarbon catalyst for carbon nanotubes, the preparation method comprising:

[0006] Providing a carbon source, a heteroatom source, a metal salt having a catalytically active component and an inert material lining;

[0007] dissolving the carbon source, the heteroatom source and the metal salt in a solvent to form a reaction solution;

[0008] The reaction liquid is transferred to the inert material lining, heated to react for a period of time, and the product is collected after cooling to obtain a nano metal / carbon catalyst powder. The nano metal / carbon catalyst powder has a CX-Me structure, wherein C represents a carbon element, X represents a heteroatom element, and Me represents a metal element. The CX-Me structure is formed by chelating the CX site with the metal nanoparticle.

[0009] In a possible implementation manner, dissolving the carbon source, the heteroatom source and the metal salt in a solvent to form a reaction solution comprises:

[0010] The carbon source, the heteroatom source and the metal salt are dissolved in water and stirred for 0.5-2 hours to obtain the reaction solution. In a possible implementation, the metal salt includes one or more of nitrate, hydrochloride, sulfate, acetate, sulfate, citrate and acetate of a catalytically active metal element.

[0011] In a possible implementation manner, the catalytically active metal element includes one or more of iron, cobalt, and nickel.

[0012] In a possible embodiment, the carbon source and the heteroatom source are homologous;

[0013] The carbon source and the heteroatom source include one or more of citric acid, melamine, triethylenetetramine, thiourea, carbonamide, and dopamine.

[0014] In a possible implementation, the heteroatom element includes one or more of nitrogen, sulfur, phosphorus, boron, and silicon. In a possible implementation, the concentration of the metal salt in the reaction solution is 0.1-1.2 mol / L;

[0015] The concentrations of the carbon source and the heteroatom source in the reaction solution are 0.6-4.0 mol / L, and the molar ratio of the carbon source to the metal salt is 1:1-10:1.

[0016] In a possible implementation manner, the material of the inert material substrate includes one or more of polytetrafluoroethylene and stainless steel.

[0017] In a possible implementation manner, the particle size of the nano metal / carbon catalyst powder is 5-12 nm.

[0018] In a possible implementation, the step of transferring the reaction solution to the inert material lining, heating the reaction solution for a period of time, and collecting the product after cooling to obtain the nano metal / carbon catalyst powder comprises:

[0019] The reaction liquid and the inert material lining are placed in a reactor for hydrothermal reaction for a period of time, cooled to room temperature, centrifuged, washed and dried to obtain the nano metal / carbon catalyst powder.

[0020] In a possible implementation manner, the heating temperature of the hydrothermal reaction is 170-260°C.

[0021] In a possible implementation manner, the reaction time of the hydrothermal reaction is 0.5-6h.

[0022] In a possible implementation manner, the drying temperature is 40-90°C.

[0023] In a possible implementation, the step of transferring the reaction solution to the inert material lining, heating the reaction solution for a period of time, and collecting the product after cooling to obtain the nano metal / carbon catalyst powder comprises:

[0024] The reaction liquid and the inert material lining are placed in a microwave environment for microwave heating, and after a period of reaction, cooled to room temperature, centrifuged, washed, and dried to obtain the nano metal / carbon catalyst powder. In a possible implementation, the heating temperature of the microwave heating is 170-240°C.

[0025] In a possible implementation manner, the reaction time of the microwave reaction is 0.5-3 h.

[0026] In a possible implementation manner, the microwave frequency of the microwave heating is 2000-3000 MHz.

[0027] In a possible implementation manner, the drying temperature is 40-90°C.

[0028] In a possible implementation manner, the nano-carbon catalyst includes nano-metal / carbon catalyst powder prepared by the above-mentioned preparation method.

[0029] In another aspect, the present application provides a method for preparing carbon nanotubes, the method comprising:

[0030] Providing a reactor with an inert atmosphere environment;

[0031] A nano metal / carbon catalyst is used as a catalyst and a hydrocarbon gas is used as a reaction source to carry out a heating reaction in a reactor to obtain a carbon nanotube product; the nano metal / carbon catalyst is prepared by the above-mentioned preparation method.

[0032] In a possible implementation manner, the heating reaction is carried out in a reactor using a nano metal / carbon catalyst as a catalyst and a hydrocarbon gas as a reaction source to obtain a carbon nanotube product, including:

[0033] The reactor is heated to a preset reaction temperature under the protection of an inert gas, and a hydrocarbon gas is introduced when the temperature is stable. The nano metal / carbon catalyst is then dispersed in an organic solvent and injected into the reactor through microflow. After a period of reaction, the hydrocarbon gas introduction is stopped, and the product is collected to obtain carbon nanotubes.

[0034] In a possible implementation manner, the preset reaction temperature is 700-900° C., and the reaction time is 0.5-1 h.

[0035] In a possible implementation manner, the heating reaction is carried out in a reactor using a nano metal / carbon catalyst as a catalyst and a hydrocarbon gas as a reaction source to obtain a carbon nanotube product, including:

[0036] The nano metal / carbon catalyst is compacted into particles and placed in the reactor. The temperature is gradually raised to a preset reaction temperature under the protection of an inert gas. When the temperature is stable, hydrocarbon gas is introduced. After a period of reaction, the introduction of hydrocarbon gas is stopped, and the product is collected to obtain carbon nanotubes. The size of the particles is 20-60 mesh.

[0037] On the other hand, the present application provides an application of carbon nanotubes prepared by the above method for preparing carbon nanotubes in conductive materials.

[0038] Based on the above technical solution, this application has the following beneficial effects:

[0039] The technical solution of the present application adopts a carbon source, a heteroatom source and a metal salt to form a reaction solution, and then heats and reacts in an inert material lining in one step to form a nano metal / carbon catalyst. It does not require complex processes and conditions, has significant advantages such as controllable, wide source of raw materials, simple process, low cost, etc., and is suitable for industrial production; and the obtained nano metal / carbon catalyst product has a uniformly distributed CX-Me structure, and CX sites are formed by heteroatom doping to serve as heteroatom traps to fix catalytically active metal nanoparticles, which can maintain stable catalytic activity at high temperatures, inhibit the agglomeration of metal nanoparticles at high temperatures, achieve uniform distribution and loading of metal catalytic active sites, and obtain a highly active nano carbon catalyst, thereby improving catalyst utilization, carbon nanotube yield and purity, and being able to prepare oligo-walled carbon nanotubes with a high aspect ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments or prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 : A schematic diagram of a process for preparing a nanocarbon catalyst for carbon nanotubes provided in an embodiment of the present application;

[0042] Figure 2 : Schematic diagram of the preparation process of nano-carbon catalyst for carbon nanotubes provided in the embodiment of the present application; DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0044] For the following defined terms, these definitions shall apply unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether or not explicitly indicated, are defined herein as modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art considers to be equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A numerical range indicated by a lower value and a higher value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0045] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0046] At present, the preparation methods of carbon nanotubes mainly include chemical vapor deposition (CVD), laser steam method, graphite arc method and hydrothermal method. The industry generally adopts chemical vapor deposition method to manufacture carbon nanotubes. This method has low temperature and is easy to control, and has high product yield and carbon purity.

[0047] Currently, carbon nanotube materials can be used as conductive agents in new energy batteries. Conductive slurry is prepared by mixing, stirring and grinding carbon nanotubes with other raw materials such as solvents and dispersants. Compared with traditional conductive agents such as carbon black and conductive graphite, carbon nanotubes have a unique hexagonal structure, excellent electrical and thermal conductivity, acid resistance and antioxidant properties, which can improve the battery's cycle life, energy density, and fast charging and discharging performance. It has been widely used in power lithium batteries with high battery performance requirements. It is worth noting that when carbon nanotubes are used as conductive agents for lithium batteries, the ash content and magnetic material content are required to be low (especially the Fe content <50PPm), and the carbon nanotubes need to be purified before use. Most of the impurities in carbon nanotubes come from catalysts. When preparing powder catalysts by conventional chemical vapor deposition, inactive metal oxides (aluminum oxide, magnesium oxide) and silicon-based materials are mostly used as carriers, and some complexing agents are used to reduce the size of active metal sites. For example, catalyst metal nanoparticles can be sparsely distributed on an inert substrate by atomic layer deposition, freeze drying, impregnation, etc. to reduce the active loading. The inert substrate includes: mesoporous silica, porous magnesium oxide and zeolite, etc., to prepare catalysts with stable metal nanoparticles of predefined sizes, and then obtain carbon nanotubes with low diameters. The catalyst is prevented from aggregating and becoming coarse during the chemical vapor deposition CVD preparation process by using spatial physical isolation and expanding the distance between particles.

[0048] The phenomenon of high-temperature sintering of metals is alleviated. However, this method has limited effect in inhibiting the aggregation of metal particles at high temperatures, and the low active metal loading will affect the carbon nanotube yield and catalyst utilization. In addition, in the process of catalytic carbon nanotube synthesis, the inert substrate will inevitably be interwoven and coated by the carbon nanotubes, resulting in excessively high metal impurity content and ash content in the obtained carbon nanotube material, which requires laborious purification procedures before it can be applied to conductive slurries, and the catalyst preparation process is also relatively complicated.

[0049] To solve at least one of the above problems, the following describes a method for preparing a nanocarbon catalyst for carbon nanotubes provided in an embodiment of the present application. This specification provides method operation steps as in the embodiment, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiment is only one way of executing the order of many steps and does not represent the only execution order. When the preparation method is actually executed, it can be executed in the order of the method shown in the embodiment or in parallel. Reference Figure 1 , the preparation method includes S1-S3:

[0050] S1: providing a carbon source, a heteroatom source, a metal salt having a catalytically active component and an inert material lining;

[0051] S2: dissolving a carbon source, a heteroatom source and a metal salt in a solvent to form a reaction solution;

[0052] S3: Transfer the reaction liquid to an inert material lining, heat and react for a period of time, collect the product after cooling, and obtain nano metal / carbon catalyst powder.

[0053] Specifically, the nano metal / carbon catalyst powder has a CX-Me structure, wherein C represents the carbon element, X represents the heteroatom element, and Me represents the metal element. The CX-Me structure is formed by chelating the CX site with the metal nanoparticles. Specifically, the nano metal / carbon catalyst powder is composed of heteroatom-doped graphite carbon, nano-sized metal or metal oxide particles, and the metal nanoparticles are uniformly dispersed on the surface of the nano carbon particles, and combined with the CX sites distributed thereon to form a CX-Me structure, which plays a role in fixing and isolating.

[0054] The above technical solution uses a carbon source, a heteroatom source and a metal salt to form a reaction solution, and then heats and reacts in an inert material lining in one step to form a nano metal / carbon catalyst. It does not require complex processes and conditions, and has significant advantages such as controllable, wide source of raw materials, simple process, and low cost. It is suitable for industrial production; and the obtained nano metal / carbon catalyst product has a uniformly distributed CX-Me structure, and CX sites are formed by heteroatom doping to serve as heteroatom traps to fix catalytically active metal nanoparticles. It can maintain stable catalytic activity at high temperatures, inhibit the agglomeration of metal nanoparticles at high temperatures, and achieve uniform distribution and loading of metal catalytic active sites, thereby obtaining a highly active nano carbon catalyst, thereby improving catalyst utilization, carbon nanotube yield and purity, and being able to prepare oligo-walled carbon nanotubes with a high aspect ratio.

[0055] Specifically, the carbon source and heteroatom source refer to materials containing carbon (C) and heteroatom (X) and capable of forming a nanocarbon skeleton having CX sites through a solvothermal reaction; the CX sites are heteroatom traps capable of chelating with metal nanoparticles. Metal salts are materials that can be mixed with carbon sources and heteroatom sources in a solvent and can generate metal nanoparticles chelated with the CX sites through a solvothermal reaction.

[0056] In some embodiments, the metal salt includes one or more of nitrates, hydrochlorides, sulfates, acetates, sulfates, citrates, and acetates of catalytically active metal elements; the use of the above-mentioned metal salts is conducive to the full mixing of metal components, carbon sources, and heteroatom sources, and improves the uniformity and amount of active sites in the catalyst product.

[0057] In some embodiments, the catalytically active metal element includes one or more of iron, cobalt, and nickel.

[0058] In some embodiments, the heteroatom elements include one or more of nitrogen, sulfur, phosphorus, boron, and silicon. The above-mentioned heteroatoms can form heteroatom traps in the product structure after a solvent thermal reaction, and can chelate metal nanoparticles to introduce heteroatoms into the carbon material to specifically capture and stabilize the metal nanoparticles. Among them, nitrogen, sulfur, boron, phosphorus, etc. can form strong coordination bonds with the metal center through their lone pair electrons, and silicon can form coordination bonds with metal nanoparticles through carrier capture, thereby anchoring the metal nanoparticles at specific positions of the carbon material skeleton, effectively preventing the aggregation and migration of metal nanoparticles, and maintaining the dispersion and high activity of metal active sites.

[0059] In some embodiments, the carbon source and the heteroatom source are homologous, that is, the same material includes both carbon and heteroatom elements. Accordingly, the carbon source and the heteroatom source include one or more of citric acid, melamine, triethylenetetramine, thiourea, carbonamide, and dopamine. The above materials can be fully mixed with the metal source and provide a suitable ratio of carbon atoms and heteroatoms to form a carbon skeleton material with a suitable distribution density and active site amount, thereby ensuring the uniformity and high activity of the distribution of metal active sites in the catalyst.

[0060] In some embodiments, S2 includes: dissolving a carbon source, a heteroatom source and a metal salt in water, stirring for 0.5-2 hours to obtain a reaction solution; the stirring temperature may be room temperature. Exemplarily, at least one of an iron salt, a cobalt salt or a nickel salt is dissolved in an appropriate amount of deionized water to form a solution of a certain concentration, and then a carbon source and a heteroatom source are added and stirred at room temperature for 0.5-2 hours to obtain a reaction solution.

[0061] Specifically, the inert material lining is used to provide a carrier combined with the catalyst, has reaction inertness in the reaction of the carbon source, the heteroatom source and the metal salt, and has chemical inertness during the growth of the carbon nanotubes, and can achieve the recyclability of the nano metal / carbon catalyst. In some embodiments, the material of the inert material substrate includes one or more of polytetrafluoroethylene and stainless steel. The inert material lining can not only ensure the original catalytic activity of the nano metal / carbon catalyst, but also improve the catalytic stability.

[0062] In some embodiments, the concentration of the metal salt in the reaction solution is 0.1-1.2 mol / L; the concentration of the carbon source and the heteroatom source in the reaction solution is 0.6-4.0 mol / L. Preferably, the concentration of the metal salt in the reaction solution is 0.6-1.0 mol / L; the concentration of the carbon source and the heteroatom source is 1.8-3.6 mol / L. In some embodiments, the molar ratio between the carbon source and the metal salt in the reaction solution is 1:1-10:1. Preferably, the molar ratio between the carbon source and the metal salt in the reaction solution is 3:1-8:1. By regulating the concentrations of the metal salt, the carbon source, and the heteroatom source to the above concentrations, the ratio of the metal source to the carbon source is regulated, so that the metal active sites in the product are evenly distributed and have a suitable density and spacing, thereby effectively alleviating the agglomeration of the metal during the high temperature reaction and improving the utilization rate of the catalyst. It should be noted that the concentration of the metal salt in the reaction solution, the concentration of the carbon source, and the concentration of the heteroatom source can be any point value in the corresponding range, which is not enumerated here.

[0063] In some embodiments, the particle size of the nano metal / carbon catalyst powder is 5-12 nm. The catalyst with the above particle size can be used to prepare oligo-walled carbon nanotubes with a high aspect ratio.

[0064] Based on some or all of the above embodiments, in some embodiments, reference Figure 2 , S3 may include: placing the reaction solution and the inert material lining in a reactor for a period of time for hydrothermal reaction, cooling to room temperature, and obtaining nano metal / carbon catalyst powder after centrifugation, washing, and drying. In this way, the catalyst product can be obtained by a simple one-pot hydrothermal reaction, the preparation process and operation flow are simple, and the product production efficiency is high. The particle size is small, and a large number of evenly distributed active metal sites (carbon atoms, heteroatoms, and metal particles) are loaded on the surface, and the catalytic effect is excellent.

[0065] In some embodiments, the heating temperature of the hydrothermal reaction is 170-260° C. Specifically, the heating temperature of the hydrothermal reaction can be any point value within the above range. By using a carbon source, a heteroatom source and a metal salt to form a reaction solution, and transferring it to the liner for a one-pot reaction, the catalyst synthesis can be achieved at a lower temperature, which is suitable for industrial large-scale production.

[0066] In some embodiments, the reaction time of the hydrothermal reaction is 0.5-6 hours; preferably, the reaction time is 0.5-3 hours; specifically, the reaction time of the hydrothermal reaction can be any point value within the above range. The one-pot method of the present application has a short reaction time and high preparation efficiency.

[0067] Specifically, a reactor may be used to carry out the hydrothermal reaction.

[0068] In some embodiments, the drying temperature is 40-90°C, preferably, the drying temperature is 40-70°C; specifically, the drying temperature can be any point value within the above range. The reaction liquid of the present application is used for the reaction, with less by-products and low drying temperature, which is energy-saving and efficient. Preferably, the drying process of the product is performed in a vacuum environment.

[0069] Based on some or all of the above embodiments, in other embodiments, S3 may include: placing the reaction liquid and the inert material lining in a microwave environment for microwave heating, reacting for a period of time, cooling to room temperature, and obtaining nano metal / carbon catalyst powder after centrifugation, washing, and drying. In this way, the catalyst product can be obtained by a simple one-pot microwave reaction, the preparation process and operation flow are simple, the reaction rate can be further accelerated, the reaction time can be shortened, the product production efficiency is high, and the catalyst particle size is small, and a large number of evenly distributed active metal sites are loaded on the surface, and the catalytic effect is excellent.

[0070] Specifically, a microwave digester may be used for microwave heating.

[0071] In some embodiments, the heating temperature of microwave heating is 170-240°C.

[0072] In some embodiments, the reaction time of the microwave reaction is 0.5-3 h.

[0073] In some embodiments, the microwave frequency of microwave heating is 2000-3000 MHz, preferably 2350-2500 MHz.

[0074] In some embodiments, the drying temperature is 40-90° C. Preferably, the drying temperature is 40-70° C. Preferably, the drying process of the product is performed in a vacuum environment.

[0075] It can be understood that the final product usually contains carbon nanotubes and catalyst materials. The remaining material after the product is calcined at a high temperature, such as 950°C for a certain period of time is called ash. In the related technology, active metals such as magnesium and aluminum oxide are often used as carriers to synthesize catalysts, resulting in a high ash content in the product after calcination. However, the present application uses graphite carbon as a carrier, and the ash content after calcination is lower, thereby improving the purity of the carbon nanotubes.

[0076] In summary, the present application mixes the carbon source, the heteroatom source and the metal source into a reaction solution, and then directly obtains the nano metal / carbon catalyst by a simple one-pot method, the particle size can reach 5-12nm, and the surface is evenly loaded with active metal sites, and the CN-Me structure is formed on the nano carbon skeleton. The heteroatom trap formed by the heteroatom doping on the catalyst can effectively fix the active metal, and can maintain stable catalytic activity at high temperatures, inhibit the agglomeration of metal nanoparticles at high temperatures, and avoid the high ash problem caused by the inert substrate in the past. In addition, by regulating the ratio of the metal source to the carbon source, a highly active catalyst can be prepared for the synthesis of high aspect ratio and few-walled carbon nanotubes. In addition, the catalyst preparation method provided by the present application has significant advantages such as adjustable, wide source of raw materials, simple process, and low cost, which is very suitable for promotion and application at the industrial level, and provides a new idea for realizing the industrial production of few-walled carbon nanotubes with high aspect ratio.

[0077] The present application also provides a nano-carbon catalyst for carbon nanotubes, characterized in that the nano-carbon catalyst comprises nano-metal / carbon catalyst powder prepared by the above-mentioned preparation method.

[0078] The present application also provides a method for preparing carbon nanotubes, the preparation method comprising:

[0079] S100, providing a reactor with an inert atmosphere environment;

[0080] S200, using a nano metal / carbon catalyst as a catalyst and a hydrocarbon gas as a reaction source to perform a heating reaction in a reactor to obtain a carbon nanotube product; the nano metal / carbon catalyst is prepared by the above-mentioned preparation method.

[0081] In some embodiments, S200 may include: heating the reactor to a preset reaction temperature under the protection of an inert gas, introducing a hydrocarbon gas when the temperature stabilizes, dispersing the nano metal / carbon catalyst in an organic solvent and injecting it into the reactor through microflow, and after a period of reaction, stopping the introduction of the hydrocarbon gas, collecting the product, and obtaining carbon nanotubes.

[0082] Specifically, microfluidic injection refers to the use of microfluidic technology to perform catalyst injection processing to achieve efficient use of catalysts.

[0083] Specifically, after the hydrocarbon gas is stopped from being introduced, the flow rate of the inert gas is increased, and a filter is arranged at the tail of the reactor to collect the carbon nanotube product.

[0084] In other embodiments, S200 may include: compacting the nano metal / carbon catalyst into particles and placing them into a reactor, gradually heating up to a preset reaction temperature under the protection of an inert gas, introducing hydrocarbon gas when the temperature stabilizes, stopping the introduction of hydrocarbon gas after a period of reaction, collecting the product, and obtaining carbon nanotubes.

[0085] Specifically, the size of the particles is 20-60 mesh. The particles made by compaction are porous particles with low density.

[0086] The present application provides an application of carbon nanotubes prepared by the above carbon nanotube preparation method in conductive materials.

[0087] The following is a specific embodiment of the present application in combination with the above technical solution:

[0088] Example 1

[0089] A preparation method of a nano-carbon catalyst with a CN-Fe structure comprises the following steps:

[0090] Step 1): 26.2 g of ammonium ferric citrate was fully dissolved in 100 mL of deionized water, and then 20 g of triethylenetetramine was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner, and reacted at 200 ° C for 1 hour under the protection of an inert gas by a microwave digestion instrument. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70 ° C for 6 hours to obtain a CN-Fe nanocarbon catalyst;

[0091] Step 2): 0.5 g CN-Fe nanocarbon catalyst is dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor is heated to 730 ° C at 10 ° C / min under the protection of nitrogen with a gas flow rate of 1000 sccm; when the temperature is stable, propylene (600 sccm) and hydrogen (100 sccm) are introduced, and the mixed solution A is injected into the reactor at a rate of 1 mL / min. After reacting for 30 minutes, propylene and hydrogen are turned off, and the nitrogen flow rate is adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate is reduced to 1000 sccm, and the reactor is gradually cooled to room temperature to obtain 12 g of carbon nanotubes with a growth rate of 23.

[0092] Through characterization, the obtained carbon nanotubes have a diameter of ≤6nm, 3-7 layers of tube wall, and a specific surface area of ​​750m2 / g.

[0093] Example 2

[0094] A preparation method of a nano-carbon catalyst with a CN / S-Fe structure comprises the following steps:

[0095] Step 1): 15 g of ammonium ferric citrate was fully dissolved in 100 mL of deionized water, and then 18 g of thiourea was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner and reacted at 220° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Fe nanocarbon catalyst.

[0096] Step 2): 0.5 g CN / S-Fe nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature was stable, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 13.5 g of carbon nanotubes with a growth factor of 26.

[0097] Through characterization, the obtained carbon nanotubes have a diameter of ≤5nm, 2-5 layers of tube wall, and a specific surface area of ​​790m2 / g.

[0098] Example 3

[0099] A preparation method of a CN / S-Co structured nanocarbon catalyst comprises the following steps:

[0100] Step 1): 13 g of cobalt citrate is fully dissolved in 100 mL of deionized water, and then 28 g of thiourea is added, and stirred at room temperature for 30 minutes to obtain a reaction solution, which is then transferred to a polytetrafluoroethylene liner, and reacted at 230° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction is completed, it is cooled to room temperature, and the reaction solution and the product are separated by centrifugation. The product is centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Co nanocarbon catalyst.

[0101] Step 2): 0.5 g CN / S-Co nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature stabilized, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 11 g of carbon nanotubes with a growth rate of 21.

[0102] Through characterization, the obtained carbon nanotubes have a diameter of ≤7nm, 3-5 layers of tube wall, and a specific surface area of ​​810m2 / g.

[0103] Example 4

[0104] A preparation method of a nano-carbon catalyst with a CN-Fe structure comprises the following steps:

[0105] Step 1): 20 g of ferric nitrate nonahydrate is fully dissolved in 150 mL of deionized water, and then 11 g of citric acid and 12.6 g of melamine are added, and stirred at room temperature for 30 minutes to obtain a reaction solution, which is then transferred to a polytetrafluoroethylene liner, and reacted at 230° C. for 1.5 h under the protection of an inert gas by a microwave digester. After the reaction is completed, it is cooled to room temperature, and the reaction solution and the product are separated by centrifugation. The product is centrifuged and washed 3-5 times with deionized water, and then treated in a vacuum drying oven at 70° C. for 6 h to obtain a CN-Fe nanocarbon catalyst.

[0106] Step 2): 0.5 g CN-Fe nanocarbon catalyst is dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor is heated to 730 ° C at 10 ° C / min under the protection of nitrogen with a gas flow rate of 1000 sccm; when the temperature is stable, propylene (600 sccm) and hydrogen (100 sccm) are introduced, and the mixed solution A is injected into the reactor at a rate of 1 mL / min. After reacting for 30 minutes, propylene and hydrogen are turned off, and the nitrogen flow rate is adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate is reduced to 1000 sccm, and the reactor is gradually cooled to room temperature to obtain 6 g of carbon nanotubes with a growth rate of 11.

[0107] Through characterization, the obtained carbon nanotubes have a diameter of ≤11nm, 5-9 layers of tube wall, and a specific surface area of ​​378m2 / g.

[0108] Example 5

[0109] A preparation method of a nano-carbon catalyst with a CN / S-Ni structure comprises the following steps:

[0110] Step 1): 29g of nickel nitrate hexahydrate is fully dissolved in 150mL of deionized water, and then 9.6g of citric acid and 24g of carbon amide are added, and stirred at room temperature for 30 minutes to obtain a reaction solution, which is then transferred to a polytetrafluoroethylene liner, and reacted at 230°C for 1.5h under the protection of an inert gas by a microwave digester. After the reaction is completed, it is cooled to room temperature, and the reaction solution and the product are separated by centrifugation. The product is centrifuged and washed 3-5 times with deionized water, and then treated in a vacuum drying oven at 70°C for 6h to obtain a CN / S-Ni nanocarbon catalyst.

[0111] Step 2): 0.5 g CN / S-Ni nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature stabilized, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 3 g of carbon nanotubes with a growth rate of 5.

[0112] Through characterization, the diameter of the obtained carbon nanotubes is ≤12nm, the tube wall has about 10 layers, and the specific surface area reaches 263m2 / g.

[0113] Example 6

[0114] A preparation method of a CN-Co structured nanocarbon catalyst comprises the following steps:

[0115] Step 1): 24.9 g of cobalt acetate tetrahydrate is fully dissolved in 100 mL of deionized water, and then 28 g of thiourea is added, and stirred at room temperature for 30 minutes to obtain a reaction solution, which is then transferred to a polytetrafluoroethylene liner, and reacted at 230° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction is completed, it is cooled to room temperature, and the reaction solution and the product are separated by centrifugation. The product is centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Co nanocarbon catalyst.

[0116] Step 2): 0.5 g CN / S-Co nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature stabilized, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 9 g of carbon nanotubes with a growth rate of 17.

[0117] Through characterization, the obtained carbon nanotubes have a diameter of ≤8nm, 5-10 layers of tube wall, and a specific surface area of ​​439m2 / g.

[0118] Example 7

[0119] A preparation method of a nano-carbon catalyst with a CN-Fe structure comprises the following steps:

[0120] Step 1): 15 g of ammonium ferric citrate was fully dissolved in 100 mL of deionized water, and then 36 g of dopamine was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner and reacted at 220° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN-Fe nanocarbon catalyst.

[0121] Step 2): 0.5 g CN-Fe nanocarbon catalyst is dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor is heated to 730 ° C at 10 ° C / min under the protection of nitrogen with a gas flow rate of 1000 sccm; when the temperature is stable, propylene (600 sccm) and hydrogen (100 sccm) are introduced, and the mixed solution A is injected into the reactor at a rate of 1 mL / min. After reacting for 30 minutes, propylene and hydrogen are turned off, and the nitrogen flow rate is adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate is reduced to 1000 sccm, and the reactor is gradually cooled to room temperature to obtain 10 g of carbon nanotubes with a growth rate of 19.

[0122] Through characterization, the obtained carbon nanotubes have a diameter of ≤6nm, 3-8 layers of tube wall, and a specific surface area of ​​720m2 / g.

[0123] Example 8

[0124] A preparation method of a nano-carbon catalyst with a CN / S-Fe structure comprises the following steps:

[0125] Step 1): 7.8 g of ammonium ferric citrate was fully dissolved in 100 mL of deionized water, and then 26 g of thiourea was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner and reacted at 220° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Fe nanocarbon catalyst.

[0126] Step 2): 0.5 g CN / S-Fe nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730° C. at 10° C. / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature stabilized, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 3.5 g carbon nanotubes with a growth rate of 6.

[0127] Through characterization, the obtained carbon nanotubes have a diameter of ≤3nm, 1-5 layers of tube wall, and a specific surface area of ​​870m2 / g.

[0128] Example 9

[0129] A preparation method of a nano-carbon catalyst with a CN / S-Fe structure comprises the following steps:

[0130] Step 1): 26 g of ammonium ferric citrate was fully dissolved in 100 mL of deionized water, and then 21 g of thiourea was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner and reacted at 220° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Fe nanocarbon catalyst.

[0131] Step 2): 0.5 g CN / S-Fe nanocarbon catalyst was dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor was heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature stabilized, propylene (600 sccm) and hydrogen (100 sccm) were introduced, and the mixed solution A was injected into the reactor at a rate of 1 mL / min. After the reaction for 30 minutes, propylene and hydrogen were turned off, and the nitrogen flow rate was adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate was reduced to 1000 sccm, and the reactor was gradually cooled to room temperature to obtain 12 g of carbon nanotubes with a growth rate of 23.

[0132] Through characterization, the obtained carbon nanotubes have a diameter of ≤8nm, 1-5 layers of tube wall, and a specific surface area of ​​650m2 / g.

[0133] Comparative Example 1

[0134] A preparation method of a nano-carbon catalyst with a CN / S-Fe structure comprises the following steps:

[0135] Step 1): 45 g of ammonium ferric citrate was fully dissolved in 150 mL of deionized water, and then 5.5 g of thiourea was added, and the mixture was stirred at room temperature for 30 minutes to obtain a reaction solution, which was then transferred to a polytetrafluoroethylene liner and reacted at 220° C. for 1 hour under the protection of an inert gas by a microwave digester. After the reaction was completed, the reaction solution and the product were separated by centrifugation, and the product was centrifugally washed with deionized water for 3-5 times, and then treated in a vacuum drying oven at 70° C. for 6 hours to obtain a CN / S-Fe nanocarbon catalyst.

[0136] Step 2): 0.5 g CN / S-Fe nanocarbon catalyst is dispersed in 30 ml of ethanol solvent to obtain a mixed solution A; the fixed bed reactor is heated to 730°C at 10°C / min under nitrogen protection with a gas flow rate of 1000 sccm; when the temperature is stable, propylene (600 sccm) and hydrogen (100 sccm) are introduced, and the mixed solution A is injected into the reactor at a rate of 1 mL / min. After reacting for 30 minutes, propylene and hydrogen are turned off, and the nitrogen flow rate is adjusted to 5000 sccm for 15 minutes; then the nitrogen flow rate is reduced to 1000 sccm, and the reactor is gradually cooled to room temperature to obtain 2 g of carbon nanotubes with a growth rate of 3.

[0137] Through characterization, it was found that the diameter of the obtained carbon nanotubes was greater than 10nm, the tube wall was greater than 10 layers, and the specific surface area reached 228m2 / g.

[0138] In combination with Examples 1-9, it can be seen that the scheme of the present application can prepare oligo-walled carbon nanotubes with a diameter of less than 12nm, a specific surface area of ​​more than 263m2 / g, and a growth rate of more than 5; by adding components, the diameter can reach less than 8nm, the specific surface area can reach more than 650m2 / g, and the growth rate can reach more than 11. In combination with Example 2 and Comparative Example 1, it can be seen that when the metal salt ratio is too high, the diameter size and the number of tube walls of the prepared carbon nanotubes increase, and the specific surface area and growth rate performance are significantly reduced, indicating that the ratio setting of the present application can significantly improve the aspect ratio of carbon nanotubes.

[0139] The embodiments described above are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0140] The above description has fully disclosed the specific implementation methods of the present application. It should be pointed out that any changes made by technicians familiar with the field to the specific implementation methods of the present application do not deviate from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not limited to the above specific implementation methods.

Claims

1. A method for preparing a nanocarbon catalyst for carbon nanotubes, characterized in that: The preparation method comprises: Providing a carbon source, a heteroatom source, and a metal salt having a catalytically active component; dissolving the carbon source, the heteroatom source and the metal salt in a solvent to form a reaction solution; The reaction liquid is transferred to an inert material lining through a dropper, heated to react for a period of time, and the product is collected after cooling to obtain a nano metal / carbon catalyst powder. The nano metal / carbon catalyst powder has a CX-Me structure, wherein C represents a carbon element, X represents a heteroatom element, and Me represents a metal element. The CX-Me structure is formed by chelating the CX site with the metal nanoparticle.

2. The preparation method according to claim 1, characterized in that: The step of dissolving the carbon source, the heteroatom source and the metal salt in a solvent to form a reaction solution comprises: The carbon source, the heteroatom source and the metal salt are dissolved in water and stirred for 0.5-2h to obtain the reaction solution.

3. The preparation method according to claim 1, characterized in that: The preparation method meets at least one of the following characteristics: The metal salt includes one or more of nitrates, hydrochlorides, sulfates, acetates, sulfates, citrates, and acetates of catalytically active metal elements; The catalytically active metal elements include one or more of iron, cobalt and nickel.

4. The preparation method according to claim 1, characterized in that: The carbon source and the heteroatom source are homologous; The carbon source and the heteroatom source include one or more of citric acid, melamine, triethylenetetramine, thiourea, carbonamide, and dopamine; The heteroatom elements include one or more of nitrogen, sulfur, phosphorus, boron and silicon.

5. The preparation method according to claim 1, characterized in that: The concentration of the metal salt in the reaction solution is 0.1-1.2 mol / L; The concentrations of the carbon source and the heteroatom source in the reaction solution are 0.6-4.0 mol / L, and the molar ratio of the carbon source to the metal salt is 1:1-10:

1.

6. The preparation method according to claim 1, characterized in that: The material of the inert material substrate includes one or more of polytetrafluoroethylene and stainless steel.

7. The preparation method according to claim 1, characterized in that: The particle size of the nano metal / carbon catalyst powder is 5-12 nm.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The step of transferring the reaction solution to the inert material lining, heating for a period of time, and collecting the product after cooling to obtain the nano metal / carbon catalyst powder comprises: The reaction liquid and the inert material lining are placed in a reactor for hydrothermal reaction for a period of time, cooled to room temperature, centrifuged, washed and dried to obtain the nano metal / carbon catalyst powder.

9. The preparation method according to claim 8, characterized in that: The hydrothermal reaction satisfies at least one of the following characteristics: The heating temperature of the hydrothermal reaction is 170-260°C; The reaction time of the hydrothermal reaction is 0.5-6h; The drying temperature is 40-90℃.

10. The preparation method according to any one of claims 1 to 7, characterized in that: The step of transferring the reaction solution to the inert material lining, heating for a period of time, and collecting the product after cooling to obtain the nano metal / carbon catalyst powder comprises: The reaction liquid and the inert material lining are placed in a microwave environment for microwave heating. After a period of reaction, the reaction liquid and the inert material lining are cooled to room temperature. The nano metal / carbon catalyst powder is obtained after centrifugation, washing and drying.

11. The preparation method according to claim 10, characterized in that: The microwave heating reaction satisfies at least one of the following characteristics: The heating temperature of the microwave heating is 170-240°C; The reaction time of the microwave reaction is 0.5-3h; The microwave frequency of the microwave heating is 2000-3000MHz; The drying temperature is 40-90℃.

12. A nanocarbon catalyst for carbon nanotubes, characterized in that: The nano-carbon catalyst comprises nano-metal / carbon catalyst powder prepared by the preparation method according to any one of claims 1 to 11.

13. A method for preparing carbon nanotubes, characterized in that: The preparation method comprises: Providing a reactor with an inert atmosphere environment; A nano metal / carbon catalyst is used as a catalyst and a hydrocarbon gas is used as a reaction source to carry out a heating reaction in a reactor to obtain a carbon nanotube product; the nano metal / carbon catalyst is prepared by the preparation method according to any one of claims 1 to 11.

14. The preparation method according to claim 13, characterized in that: The method of using nano metal / carbon catalyst as catalyst and hydrocarbon gas as reaction source to heat and react in a reactor to obtain carbon nanotube products comprises: The reactor is heated to a preset reaction temperature under the protection of an inert gas, a hydrocarbon gas is introduced when the temperature is stable, and then the nano metal / carbon catalyst is dispersed in an organic solvent and injected into the reactor through microflow. After a period of reaction, the hydrocarbon gas is stopped, and the product is collected to obtain carbon nanotubes. The preset reaction temperature is 700-900° C., and the reaction time is 0.5-1 h. or, The nano metal / carbon catalyst is compacted into particles and placed in the reactor. The temperature is gradually raised to a preset reaction temperature under the protection of an inert gas. When the temperature is stable, hydrocarbon gas is introduced. After a period of reaction, the introduction of hydrocarbon gas is stopped, and the product is collected to obtain carbon nanotubes. The size of the particles is 20-60 mesh.

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