CN117819534B

CN117819534B - A high-purity single-walled carbon nanotube, its preparation method and system

Info

Publication number: CN117819534B
Application number: CN202311812401.2A
Authority: CN
Inventors: 陈名海; 朱嘉庆; 冯尉强; 常艺
Original assignee: Jiangxi Copper Technology Research Institute Co ltd
Current assignee: Jiangxi Copper Technology Research Institute Co ltd
Priority date: 2023-12-26
Filing date: 2023-12-26
Publication date: 2025-12-02
Anticipated expiration: 2043-12-26
Also published as: CN117819534A

Abstract

The invention belongs to the technical field of new materials, and particularly relates to a high-purity single-walled carbon nanotube, a preparation method and a system thereof. The method utilizes the high temperature condition of a plasma arc to evaporate the catalyst material floating on the surface of the liquid anode to form fine catalyst particles, combines the catalyst particles with an organic carbon source which is cracked at the same time, catalytically grows into single-walled carbon nanotubes, and is discharged out of a reaction furnace along with tail gas to obtain a final product. The method effectively avoids the defects of insufficient service life of the graphite crucible, catalyst metal pollution and uncontrollable catalyst concentration in the reaction, obviously improves the purity and the preparation efficiency of the product, is an effective means for preparing high-quality single-wall carbon nanotubes in a large scale, and has great economic value.

Description

High-purity single-walled carbon nanotube, preparation method and system

Technical Field

The invention belongs to the technical field of new materials, and particularly relates to a high-purity single-walled carbon nanotube, a preparation method and a system thereof.

Background

The single-wall carbon nano tube is a hollow tubular one-dimensional nano material formed by sp2 hybridized C-C covalent bonds, and because of the high crystallinity and the large-curvature structure of the surface, the potential barrier required to be spanned in the preparation growth process is far higher than that of the multi-wall carbon nano tube, so that the large-scale efficient preparation of the single-wall carbon nano tube still has a great challenge. The existing preparation method mainly comprises an arc ablation method, a laser method, a chemical vapor deposition method, a plasma method and the like. Wherein, compared with the chemical vapor deposition method, the single-wall carbon nano tube prepared by the laser method, the plasma method and the electric arc method based on the high temperature technology has higher crystallinity. However, due to the complex equipment system and high energy consumption, most single-walled carbon nanotube preparation technologies based on high temperature technology only stay at laboratory level.

The arc method takes a graphite rod filled with mixed powder of Y/Ni, feS and carbon powder as an anode, initiates an arc between a cathode and the anode, evaporates solid components of the anode to consume the anode through high temperature of the arc, and simultaneously rapidly generates single-wall carbon nanotubes in the process of outward diffusion. Because most of the products are deposited on the inner wall of the reaction cavity, the anode is continuously consumed, and most of the products can only be prepared in a batch mode. Although there have been many studies to overcome this disadvantage by continuously supplementing the anode rod, continuous mass production still has great difficulty. The plasma method adopts the steps that a carbon source and a catalyst pass through the middle of a plasma torch and rapidly pass through a high-temperature region, and a carbon nano tube product is generated in the air flow descending stage. In the plasma method, a plasma arc is generated inside an electrode gun, and the electrode gun is blown out by a high-speed air flow, and the service life of the electrode is ensured by using a high-power cold zone mode. However, the most restrictive factor of the industrialization of the method is the problem of electrode life, and the anode burning loss is too fast, so that the continuous operation is difficult, and the cost is high. In the prior art, catalyst metal placed in a graphite crucible is vaporized by a plasma arc to generate catalyst nano particles, and the catalyst nano particles are combined with a cracked carbon source to generate single-walled carbon nanotubes. The method is characterized in that the catalyst preparation and the carbon nano tube growth are placed in the same reaction chamber, and the efficient preparation is realized by utilizing the ultrahigh heat source evaporation, cracking and plasma activation actions of a plasma arc. However, the anode structure has obvious defects that firstly, iron and graphite used as a catalyst can lead carbon to be dissolved and diffused into the iron liquid at high temperature, so that the iron liquid can continuously erode a graphite crucible, the service life of the anode crucible is reduced, the catalyst is polluted, secondly, a large amount of catalyst is placed in the graphite crucible, a large amount of catalyst metal is evaporated, generation of ultrafine catalyst nano particles is not facilitated, a large amount of large particles are easily formed in collision, generation of single-wall carbon nano tubes is not facilitated, and thirdly, a large amount of molten iron liquid has a certain dissolving capacity for carbon cracked in the atmosphere, and the utilization rate of gaseous carbon sources is reduced.

Disclosure of Invention

The invention discloses a high-purity single-walled carbon nanotube, a preparation method and a system thereof, which are used for solving any of the technical problems and other potential problems in the prior art.

In order to solve the problems, the technical scheme of the invention is that the preparation method of the high-purity single-walled carbon nanotube comprises the steps of evaporating a catalyst material floating on the surface of a liquid anode to form fine catalyst particles by utilizing the high temperature condition of a plasma arc, combining the catalyst particles with an organic carbon source which is simultaneously cracked, catalyzing and growing the catalyst particles into the single-walled carbon nanotube, and discharging the single-walled carbon nanotube along with tail gas out of a reaction furnace to obtain the high-purity single-walled carbon nanotube.

Further, the preparation method specifically comprises the following steps:

s1) under the protection of inert gas, introducing plasma arc gas from a cathode of a plasma arc furnace, energizing and exciting to generate a plasma arc, melting anode metal in a graphite crucible into a liquid state, and continuously heating to a set temperature;

s2) firstly, conveying catalyst metal powder to the surface of the liquid anode metal, and forming a catalyst metal layer on the surface of the liquid anode metal;

And S3) mixing the carbon source gas, the cocatalyst and the carrier gas, introducing the mixture into a plasma arc furnace, combining the cracked organic carbon source with catalyst particles formed by evaporation, and catalytically growing the mixture into single-walled carbon nanotubes, wherein the single-walled carbon nanotubes continuously discharge the single-walled carbon nanotubes out of the reaction furnace along with tail gas, thereby obtaining the high-purity single-walled carbon nanotubes.

Further, the flow rate of the plasma arc gas in the S1) is 1L/min-200L/min;

The power of the plasma arc furnace is 10-500kW, the current is 100-10000A, and the voltage is 1-200V;

the set temperature is 700-1800 ℃;

The anode metal is copper or copper-iron alloy.

Further, the inert gas in S1) is any one of nitrogen, argon and helium;

the plasma arc gas is any one, two or three of nitrogen, argon, helium, hydrogen and steam mixed gas according to any mixing proportion;

The content of the iron in the copper-iron alloy is 1-5wt%, the height of the anode metal layer is 5-35cm, and the diameter is 30-200cm.

Further, the particle size of the catalyst metal powder in the S2) is 50-350 meshes, the input flow is 0.5-200g/min, the thickness of the catalyst on the surface of the liquid anode metal is kept to be 0.01-5mm, and the diameter is not more than 200cm.

Further, the catalyst metal powder is iron, cobalt and nickel powder or alloy powder formed by the iron, cobalt and nickel powder and molybdenum, tungsten, tantalum, niobium, hafnium, chromium, vanadium and zirconium high-melting-point metals.

Further, the volume of the carbon source gas in the S3) is 5-30%;

the carrier gas comprises hydrogen and inert gas, wherein the volume of the hydrogen is 0.1-50%, and the balance is the inert gas;

the flow rate of the carbon source gas and the carrier gas is 1L/min-500L/min;

the molar ratio of the cocatalyst to the catalyst metal powder is 20:1-1:1.

Further, the cocatalyst is any one of sulfur powder, selenium powder, thiophene or hydrogen sulfide;

the carbon source gas is any one of methane, ethylene, acetylene, propylene or propane;

The inert gas is one or more of nitrogen, argon or helium.

Another object of the present invention is to provide a system for implementing the above preparation method, comprising a plasma arc furnace body, a graphite crucible, a plasma arc furnace cathode and an anode metal;

The anode metal is arranged in the graphite crucible, the graphite crucible is arranged at the bottom of the furnace body of the plasma arc furnace, and the cathode of the plasma arc furnace is arranged vertically above the graphite crucible;

A reaction gas inlet and a catalyst feed inlet are formed in the side wall of one side of the plasma arc furnace body, a discharge port is formed in the side wall of the other side of the plasma arc furnace body, and the reaction gas inlet, the catalyst feed inlet and the discharge port are all positioned above the graphite crucible;

and the inner diameter of the graphite crucible is not less than four fifths of the inner diameter of the plasma arc furnace body.

The high-purity single-walled carbon nanotube is prepared by the preparation method.

The preparation method has the beneficial effects that by adopting the technical scheme, the preparation method of the invention sets the current-voltage parameters, the arc striking gas composition, the flow rate, the arc length and other structural parameters of the plasma arc, realizes the control of the impact force of the arc on the liquid anode, effectively avoids the pollution of the catalyst caused by the impact sputtering of the liquid metal anode to the upper end of the catalyst layer and the evaporation of the arc, and reduces the activity of the catalyst and the quality of products;

Because the density of the anode metal is higher than that of the catalyst metal, two-phase incompatible liquid metal is formed by melting at the high temperature of the plasma arc, so that the catalyst metal floats on the anode metal to form a uniform thin-layer catalyst, the anode surface is smooth, the stability of the plasma arc is improved, the dissolution of a large amount of catalyst to a gaseous carbon source cracking product is avoided, and the utilization rate of the carbon source is improved;

At the same time, under the high temperature formed by the plasma arc, the liquid anode metal floats on the surface of the melt of the metal anode to isolate the contact between the catalyst metal and the graphite crucible, so that the mutual diffusion and dissolution of graphite and the catalyst metal are avoided, and the erosion of the catalyst melt to the graphite crucible and the pollution of graphite to the catalyst metal are also avoided. Meanwhile, the anode metal, graphite and catalyst metal have no obvious dissolution and alloying effects, no corrosion to a graphite crucible, no obvious pollution to catalyst metal, good conductivity is maintained, stable operation of a plasma anode is ensured, the operation life of a system is obviously prolonged, and the service life of the anode can reach 10 days;

Based on the structure, the catalyst can be continuously, quantitatively and controllably added through the powder feed inlet, the dosage and the evaporation amount of the catalyst are effectively controlled, large particles formed by collision and aggregation of particles due to massive evaporation are avoided, the activity and the utilization rate of the catalyst are improved, and the purity of the product is obviously improved to 80% at most.

Drawings

Fig. 1 is a schematic structural diagram of a preparation system of a high purity single-walled carbon nanotube according to the present invention.

Fig. 2 is a scanning electron micrograph of single-walled carbon nanotubes prepared in example 1 of the present invention.

FIG. 3 is a Raman spectrum of a single-walled carbon nanotube prepared in example 1 of the present invention.

FIG. 4 is a thermogravimetric analysis of single-walled carbon nanotubes prepared in example 1 of the present invention.

Fig. 5 is a scanning electron micrograph of single-walled carbon nanotubes prepared in comparative example 1.

Fig. 6 is a raman spectrum of the single-walled carbon nanotube prepared in comparative example 1.

FIG. 7 is a thermogravimetric analysis curve of the single-walled carbon nanotube prepared in comparative example 1.

In the figure:

1. graphite crucible, anode metal, catalyst metal, reaction gas inlet, catalyst inlet, plasma arc furnace body, cathode, heat insulating protecting layer and discharge port.

Detailed Description

The invention will be further described with reference to the accompanying drawings and specific examples.

As shown in FIG. 1, the preparation system of the high-purity single-walled carbon nanotubes comprises a plasma arc furnace body 6, a graphite crucible 1, a plasma arc furnace cathode 7 and anode metal 2;

Wherein the anode metal 2 is arranged in the graphite crucible 1, the graphite crucible 1 is arranged at the bottom of the plasma arc furnace body 6, and the plasma arc furnace cathode 7 is arranged vertically above the graphite crucible 1;

A reaction gas inlet 4 and a catalyst feed inlet 5 are formed in the side wall of one side of the plasma arc furnace body 6, a discharge outlet 9 is formed in the side wall of the other side, and the reaction gas inlet 4, the catalyst feed inlet 5 and the discharge outlet 9 are all positioned above the graphite crucible 1;

And the inner diameter of the graphite crucible 1 is not less than four fifths of the inner diameter of the plasma arc furnace body 6.

The preparation method of the preparation system adopting the high-purity single-walled carbon nanotube comprises the following steps:

S1) under the protection of inert gas, introducing plasma arc gas from a cathode 7 of a plasma arc furnace, wherein the flow rate of the plasma arc gas is 1L/min-200L/min, generating a plasma arc by electrifying and exciting, melting anode metal 2 in a graphite crucible 1 into a liquid state, and continuously heating to 700-1800 ℃;

S2) firstly, conveying catalyst metal 3 powder to the surface of the liquid anode metal 2, and forming a catalyst metal layer on the surface of the liquid anode metal 2;

the particle size of the catalyst metal powder is 50-350 meshes, the input flow is 0.5-200g/min, the thickness of the catalyst on the surface of the liquid anode metal is kept to be 0.01-5mm, and the diameter is not more than 200cm;

The anode metal has no obvious mutual dissolving and alloying effects with graphite and catalyst metal at high temperature, the density of the catalyst metal is smaller than that of the anode metal, and the catalyst metal can be gold, platinum, silver, copper and copper-iron alloy, preferably copper or copper-iron alloy, the iron content of the copper-iron alloy is 1-5%, the height of the anode metal layer is 5-35cm, and the diameter of the anode metal layer is 30-200cm.

The catalyst metal powder can be iron, cobalt, nickel powder or alloy powder formed by high-melting point metals such as molybdenum, tungsten, tantalum, niobium, hafnium, chromium, vanadium and zirconium, and the like, preferably iron powder and ferromolybdenum alloy powder, the particle size is 50-350 meshes, the input flow is 0.5-200g/min, the thickness of the catalyst on the surface of the liquid anode metal is kept to be 0.01-5mm, and the diameter is not more than 200cm.

The carbon source gas is any one of methane, ethylene, acetylene, propylene or propane, and the carrier gas is a mixed gas of nitrogen, argon, helium and hydrogen;

Wherein the volume of the carbon source gas is 5-30%, the volume of the hydrogen is 0.1-50%, the balance is inert gas, and the flow is 1L/min-500L/min;

The catalyst promoter is any one of sulfur powder, selenium powder, thiophene, hydrogen sulfide and the like, and the molar ratio of the catalyst to the catalyst promoter is 1:1-20:1.

Example 1

The method comprises the steps of using a plasma arc furnace with power of 50kW, current of 1000A and voltage of 50V, introducing plasma arc gas argon with the power of 5L/min from a cathode of the plasma arc furnace under the protection of argon, energizing and exciting to generate plasma arc, melting anode metal copper-4% ferroalloy placed in a graphite crucible into a liquid state, heating a hearth to 1200 ℃, conveying catalyst metal powder to the surface of the liquid anode metal, wherein the catalyst metal powder is iron-molybdenum alloy powder with particle size of 100 meshes, powder feeding flow of 5g/min, then introducing carbon source gas, cocatalyst and carrier gas for mixing, wherein the components are methane of 10%, hydrogen of 20%, argon of 70%, total gas flow of 20L/min, the cocatalyst is hydrogen sulfide, the molar ratio of the catalyst metal to the cocatalyst is 10:1, continuously reacting in the arc furnace, and collecting the product along with tail gas at a discharge hole to obtain the final single-wall carbon nanotube product. FIG. 2 shows a scanning electron micrograph of the prepared product, FIG. 3 shows a Raman spectrum of the prepared product, and FIG. 4 shows a thermogravimetric analysis curve of the prepared product.

Example 2

The method comprises the steps of using a plasma arc furnace with power of 500kW, current of 10000A and voltage of 50V, introducing 200L/min of plasma arc gas and argon from a cathode of the plasma arc furnace under the protection of argon, energizing and exciting to generate plasma arc, melting anode metal copper in a graphite crucible into a liquid state, heating a hearth to 1800 ℃, conveying catalyst metal powder to the surface of the liquid anode metal, wherein the catalyst metal powder is iron powder with particle size of 50 meshes, feeding the powder with flow of 200g/min, then introducing carbon source gas, a cocatalyst and carrier gas for mixing, wherein the components are methane 30%, hydrogen 50%, argon 20%, and total gas flow of 200L/min, the cocatalyst is sulfur powder, the molar ratio of the catalyst metal to the cocatalyst is 20:1, continuously conducting the reaction in the arc furnace, and collecting the product along with tail gas at a discharge hole to obtain the final single-wall carbon nanotube product.

Example 3

The method comprises the steps of using a plasma arc furnace with power of 10kW, current of 100A and voltage of 100V, introducing plasma arc gas of argon with the power of 1L/min from a cathode of the plasma arc furnace under the protection of argon, energizing and exciting to generate plasma arc, melting anode metal copper-4% ferroalloy placed in a graphite crucible into a liquid state, heating a hearth to 700 ℃, conveying catalyst metal powder to the surface of the liquid anode metal, wherein the catalyst metal powder is iron powder with particle size of 350 meshes, powder conveying flow of 0.5g/min, introducing carbon source gas, cocatalyst and carrier gas for mixing, wherein the components are methane of 5%, hydrogen of 0.1%, argon of 94.9%, total gas flow of 1L/min, the cocatalyst is thiophene, the molar ratio of the catalyst metal to the cocatalyst is 15:1, continuously reacting in the arc furnace, and collecting the product along with tail gas at a discharge hole to obtain a final single-wall carbon nanotube product.

Comparative example 1

Comparative example 1 the basic process parameters were essentially the same as in example 1, except that the catalyst feed was omitted and the anode metal was replaced entirely with the catalyst metal directly, allowing the catalyst metal to be placed directly in the graphite crucible.

The method comprises the steps of using a plasma arc furnace with power of 50kW, current of 1000A and voltage of 50V, introducing plasma arc gas argon with the power of 5L/min from a cathode of the plasma arc furnace under the protection of argon, energizing and exciting to generate plasma arc, melting a catalyst iron-molybdenum alloy placed in a graphite crucible into a liquid state, heating a hearth to 1200 ℃, then introducing carbon source gas, a cocatalyst and carrier gas for mixing, wherein the components comprise 10% of methane, 20% of hydrogen, 70% of argon and 20L/min of total gas flow, the cocatalyst is hydrogen sulfide, the flow is the same as that of the embodiment 1, continuously carrying out the reaction in the arc furnace, and collecting the product along with tail gas at a discharge hole to obtain the final single-wall carbon nanotube product. FIG. 5 shows a scanning electron micrograph of the resulting product, FIG. 6 shows a Raman spectrum of the resulting product, and FIG. 7 shows a thermogravimetric analysis of the resulting product.

Data result comparison

The high-purity single-walled carbon nanotubes, the preparation method and the system provided by the embodiment of the application are described in detail. While the foregoing examples have been provided to assist those of ordinary skill in the art in understanding the methods and concepts underlying the application, those skilled in the art will recognize that there may be variations in the embodiments and applications of the application in light of the foregoing, and that the application is not to be construed as limited to what is described herein.

Certain terms are used throughout the description and claims to refer to particular components. Those of skill in the art will appreciate that a hardware manufacturer may refer to the same component by different names. The description and claims do not take the form of an element differentiated by name, but rather by functionality. As referred to throughout the specification and claims, the terms "comprising," including, "and" includes "are intended to be interpreted as" including/comprising, but not limited to. By "substantially" is meant that within an acceptable error range, a person skilled in the art is able to solve the technical problem within a certain error range, substantially achieving the technical effect. The description hereinafter sets forth a preferred embodiment for practicing the application, but is not intended to limit the scope of the application, as the description is given for the purpose of illustrating the general principles of the application. The scope of the application is defined by the appended claims.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such product or system. Without further limitation, an element defined by the phrase "comprising one of the elements" does not exclude the presence of additional identical elements in a commodity or system comprising the element.

It should be understood that the term "and/or" as used herein is merely an association relationship describing the associated object, and means that there may be three relationships, e.g., a and/or B, and that there may be three cases where a exists alone, while a and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

While the foregoing description illustrates and describes the preferred embodiments of the present application, it is to be understood that the application is not limited to the forms disclosed herein, but is not to be construed as limited to other embodiments, and is capable of numerous other combinations, modifications and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, either as a result of the foregoing teachings or as a result of the knowledge or technology of the relevant art. And that modifications and variations which do not depart from the spirit and scope of the application are intended to be within the scope of the appended claims.

Claims

1. The preparation method is characterized in that the preparation method utilizes the high temperature condition of a plasma arc to evaporate catalyst materials floating on the surface of a liquid anode to form fine catalyst particles, the fine catalyst particles are combined with an organic carbon source which is simultaneously cracked to form single-walled carbon nanotubes by catalytic growth, and the single-walled carbon nanotubes are discharged out of a reaction furnace along with tail gas to obtain the high-purity single-walled carbon nanotubes, and the preparation method specifically comprises the following steps:

the anode metal is copper or copper-iron alloy;

The content of the copper-iron alloy iron is 1-5wt%, the height of the anode metal layer is 5-35cm, and the diameter is 30-200cm;

The particle size of the catalyst metal powder is 50-350 meshes, the input flow is 0.5-200 g/min, the thickness of the catalyst on the surface of the liquid anode metal is kept to be 0.01-5mm, and the diameter is not more than 200cm;

The catalyst metal powder is iron, cobalt and nickel powder or alloy powder formed by the iron, cobalt and nickel powder and molybdenum, tungsten, tantalum, niobium, hafnium, chromium, vanadium and zirconium high-melting-point metals;

2. The method according to claim 1, wherein the flow rate of the plasma arc gas in S1) is 1L/min to 200L/min;

the power of the plasma arc furnace is 10-500 kW, the current is 100-10000A, and the voltage is 1-200V;

The set temperature is 700-1800 ℃.

3. The method according to claim 2, wherein the inert gas in S1) is any one of nitrogen, argon and helium;

the plasma arc gas is any one, two or three of nitrogen, argon, helium, hydrogen and steam mixed gas according to any mixing proportion.

4. The method according to claim 1, wherein the carbon source gas in S3) occupies 5 to 30% by volume;

The flow rate of the carbon source gas and the carrier gas is 1L/min-500L/min;

the molar ratio of the cocatalyst to the catalyst metal powder is 20:1-1:1.

5. The preparation method according to claim 4, wherein the cocatalyst is any one of sulfur powder, selenium powder, thiophene or hydrogen sulfide;

The inert gas is one or more of nitrogen, argon or helium.

6. A system for carrying out the process according to any one of claims 1 to 5, wherein the system comprises a plasma arc furnace body, a graphite crucible, a plasma arc furnace cathode and an anode metal;

7. A high purity single wall carbon nanotube, wherein the high purity single wall carbon nanotube is prepared by the preparation method of any one of claims 1-5.