CN1673073A - Single-wall carbon nanotube synthesizing process - Google Patents
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Abstract
The present invention discloses the single-wall carbon nanotube synthesizing process. Inside a reactor and under the action of catalyst containing transition metal or other alloy particle, carbon-containing material gas with water vapor in 0.01-3 vol% is decomposed catalytically at high temperature. In the technological scheme of the present invention, the addition of water vapor into the carbon-containing material gas can prevent the generation of amorphous carbon and multiple-wall carbon nanotube to obtain high purity single-wall carbon nanotube.
Description
Technical Field
The invention belongs to the technical field of nanometer, and particularly relates to a method for efficiently preparing a high-purity single-walled carbon nanotube.
Background
Since the discovery of carbon nanotubes by Iijima in 1991, the research on carbon nanotubes has been rapidly developed, and has become one of the most popular fields of material science in recent years due to the discovery of many unique and superior properties of carbon nanotubes. Carbon nanotubes have great potential for use in applications, including the following areas: electrically conductive and high strength composite materials, energy storage and conversion devices (fuel cells), sensors, field emission displays and sources, hydrogen storage materials, nano-semiconductor devices, microprobes and micro-wires, and the like.
Carbon nanotubes are divided into multi-walled and single-walled carbon nanotubes, and in many applications, single-walled carbon nanotubes have superior properties to multi-walled carbon nanotubes, such as smaller diameter single-walled carbon nanotubes, fewer defects, higher strength, and better electrical conductivity.
The multi-wall carbon nano-tube with higher purity uses methane and C at present2-C8The carbon-containing raw material gases such as hydrocarbon, methanol, ethanol, carbon monoxide and the like can be prepared on a relatively large scale and the cost is not high by catalytic decomposition at high temperature (600-1200 ℃) in the presence of a catalyst containing transition metals such as iron, cobalt, nickel, molybdenum and the like. However, the preparation of the single-walled carbon nanotube is much more difficult than that of the multi-walled carbon nanotube, and a method for efficiently producing the single-walled carbon nanotube in a large scale at a low cost is still lacked so far, so that the popularization and the application of the single-walled carbon nanotube are limited.
The literature reports that single-walled carbon nanotubes can be produced by laser evaporation of carbon (Thoss, A. et al, Science, 273: 483, 1996) and graphite electrode arc discharge (Journet et al, Nature, 388: 756, 1997), but other forms of carbon products often coexist and are very energy intensive and low yielding and cannot be produced continuously.
The catalytic cracking method is a promising method for manufacturing single-walled carbon nanotubes on a large scale at low cost. Dai et Al (Chemical Physics Letter, 1996, 260: 471) first reported using CO as the feed gas, via Al2O3The single-walled carbon nano-tube is prepared by catalytic decomposition of a fixed bed loaded with a molybdenum catalyst at 1200 ℃. But the preparation conditions are harsh, the product purity is not high, and the yield is very low. Cheng et al (Applied Physics Letters, 1998, 72{25}3282) reported that single-walled carbon nanotubes were produced by benzene cracking at 1100-.
Smalley et Al in US patent US 6692717 report using CO and ethylene as raw material gas, loading Al on quartz boat2O3Single-wall carbon nanotubes can be obtained by reaction at 800-850 ℃ in a tube reactor loaded with a catalyst of transition metals such as Fe, Mo and the like, but the purity is not high and the yield is low. Smalley et al, US6761870, report using high pressure (about 30 atm) CO as the starting material, in a horizontal suspension bed of Fe (CO)5、Ni(CO)4、Fe(C5H5)2Is used as catalyst precursor, and the metal nano particle without carrier obtained by thermal decomposition is used as catalyst, and the single-wall carbon nano tube is obtained by catalytic decomposition at about 1000 ℃, but the purity and the yield are also very low.
David Moy et al in U.S. Pat. No. 5, 6827919 report that single-walled carbon nanotubes can be obtained by catalytic decomposition using molecules containing 1-6 carbon atoms as raw material gas and unsupported transition metal aerosol particles obtained by decomposition of a compound containing a transition element as a catalyst, but the purity is less than 50%, and a large amount of amorphous carbon and multi-walled carbon nanotubes exist.
Lessack et al, in Chinese patent CN1360558, reported the use of a carbon-containing gas such as CO as a starting material and SiO2When the catalyst is used as a carrier, VIII metal except iron such as Co, Ni and the like and VIB metal such as Mo and the like are loaded to be used as catalysts, the single-walled carbon nanotube can be obtained by catalytic decomposition, but the yield is very low, and the purity is mostly less than 90%.
Zheng and et al reported in CN1403371 that single-walled carbon nanotubes can be obtained by carrying tetraethoxysilane and ferrocene into a reactor with hydrogen-containing carrier gas and reacting at 900-1200 ℃, but the carbon-containing raw material gas is expensive, and SiO in the product is SiO2The content is nearly half, the single-walled carbon nano tube is obtained only by removing with hydrofluoric acid, and the yield is only 8 percent at most.
The patent CN1530321 reports that single-wall carbon nanotubes can be obtained by using a molybdenum boat-loaded tubular reactor, using magnesium oxide or alumina oxide loaded with cobalt, molybdenum, rare earth and alkaline earth element as catalysts, and using mixed gas of methane and hydrogen as raw materials, and carrying out catalytic decomposition reaction at 700 plus 1000 ℃ for about 1 hour, but the space-time yield is not high, and the product contains multiple-wall tubes.
Zhuhongwei et al reported in CN1176014, by using a vertical bed floating catalytic cracking method, using n-hexane as a carbon source, ferrocene as a catalyst, and thiophene as an additive to prepare a reaction solution, introducing the reaction solution into a reactor along with hydrogen in a vapor form, and performing catalytic decomposition at 1000-1200 ℃ to obtain an ultra-long single-walled carbon nanotube bundle with the length of 20cm, but the purity is very low, and the single-walled tube only accounts for about 5% of the total carbon product.
From the above documents and patent reports, the prior single-walled carbon nanotube preparation has the problems of low yield, low product purity, high manufacturing cost and the like, and is difficult to produce and apply on a large scale at a low price.
Disclosure of Invention
The invention aims to provide a method for easily synthesizing high-purity single-walled carbon nanotubes.
The technical scheme of the invention is as follows:
a method for synthesizing single-walled carbon nanotubes comprises the step of decomposing a carbon-containing raw material gas at high temperature in a reactor under the action of a catalyst containing transition metal or alloy particles thereof, wherein water vapor accounting for 0.01-3% of the volume of the carbon-containing raw material gas is added into the carbon-containing raw material gas.
In the method for synthesizing the single-walled carbon nanotube, the carbon-containing raw material gas is selected from molecules containing 1-8 carbon atoms or a mixture thereof. A preferred carbon-containing feed gas is methane. The carbon-containing feed gas may also contain nitrogen, argon or hydrogen as a diluent gas, and a sulfur-containing compound as an auxiliary.
In the method for synthesizing the single-walled carbon nanotube, the reaction temperature of the catalytic decomposition is 600-1200 ℃.
In the method for synthesizing single-walled carbon nanotubes, the catalyst containing the transition metal or the alloy particles thereof is a catalyst containing iron, cobalt, nickel, molybdenum and tungsten or alloy particles thereof supported by an oxide carrier, or a catalyst containing iron, cobalt, nickel, molybdenum or tungsten or alloy particles thereof supported by an unsupported carrier. The carrier-loaded iron, cobalt, nickel, molybdenum or tungsten catalyst is MgO or Al with high specific surface area2O3Or SiO2Or the combination of the carrier and the compound loaded with iron, cobalt, nickel, molybdenum or tungsten is obtained by heating, decomposing and reducing. The unsupported iron, cobalt, nickel, molybdenum or tungsten or alloy particles thereof are obtained by heating and decomposing or reducing compound steam of iron, cobalt, nickel, molybdenum or tungsten in a reactor. The iron, cobalt, nickel, molybdenum or tungsten compound refers to their oxides, chlorides, nitrates, sulfates, organic acid salts, carbonyl compounds, cyclopentadienyl compounds or acetylacetoneA compound is provided.
In the method for synthesizing the single-walled carbon nanotube, the reactor is a fluidized bed reactor, a suspended bed reactor or a fixed bed reactor.
By adopting the technical scheme of the invention, when the carbon-containing raw gas is decomposed into carbon products by the catalyst by adding a trace amount of water into the carbon-containing raw gas, the trace amount of water can prevent the generation of amorphous carbon and multi-walled carbon nanotubes and promote the generation of single-walled carbon nanotubes.
The mechanism of the present invention is analyzed in detail below.
Most of the previous methods for preparing single-walled carbon nanotubes by catalytic cracking simultaneously produce considerable amounts of amorphous carbon and multi-walled carbon nanotubes.
Among the allotropes of carbon, the graphite structure is the most stable. Amorphous carbon can be considered as a random connection of very small graphitic crystallites. The multi-wall carbon nano tube is a cylinder formed by curling a multilayer graphite carbon six-ring structure with the diameter of several nanometers to dozens of nanometers, and the top of the multi-wall carbon nano tube is a multilayer cap similar to a fullerene structure. The single-walled carbon nanotube is a cylinder formed by rolling a single-layer graphite carbon six-ring structure with the diameter of 0.7-3nm, and the top of the single-walled carbon nanotube is provided with a fullerene-like cap.
The conditions and mechanism for the formation of single-walled carbon nanotubes are such that particles of transition metals (Fe, Co, Ni, Mo, W) or their alloys, which can catalytically decompose a carbon-containing feed gas, are present, the size of which is about 1-3nm, or the metal particles are large but affected by additives (such as sulfides), and the surface of the particles is divided into metal surface regions of about 1-3 nm. The carbon-containing raw material gas is decomposed at high temperature on the surface of the transition metal particles to generate carbon, the carbon is diffused and dissolved into the metal particles to be saturated and then is separated out on the surface to form a cap with a fullerene-like structure with lower energy, in order to reduce the energy, a metal-carbon bond is formed on the periphery of the cap, and when the carbon is continuously increased to supply, the carbon grows upwards along the periphery according to a graphite layer structure to form a single-wall carbon nano tube. On the surface of transition metal or their alloy particle less than about 3nm, only single-wall carbon nanotube can be grown, graphite, amorphous carbon and multi-wall carbon nanotube can be not produced as long as the decomposition carbon supply speed of carbon-containing raw gas does not exceed the growth speed of single-wall carbon nanotube. The graphite structure is most stable, but the peripheral bond force is unsaturated, the dangling bond with high bond energy can exist stably only when enough large graphite flakes are generated and the energy rise caused by the peripheral dangling bond is negligible, the carbon-containing raw material gas decomposes and separates out carbon on the surface of small nano transition metal particles, and the graphite with a stable structure is difficult to generate because when the graphite flakes grow to exceed the size of metal nano particles, metal-carbon bonds can not be generated on the periphery, and the peripheral dangling bond is eliminated to reduce energy. When the transition metal particles in the catalyst exceed 3nm but are less than tens of nanometers, the multi-wall carbon nano-tube can be produced by the high-temperature catalytic decomposition of the carbon-containing feed gas, and graphite is not produced. When the transition metal particles in the catalyst are too large (more than tens of nanometers), the carbon-containing feed gas is catalytically decomposed at high temperature on the surface thereof to easily generate amorphous carbon. Amorphous carbon can also be produced when carbon-containing feed gases are thermally decomposed at high temperatures or decomposed at the catalyst support surface and reactor surface to produce carbon at rates exceeding the production rates of multi-walled and single-walled carbon nanotubes.
From the above analysis, it can be seen that single-walled carbon nanotubes are a metastable state in carbon allotropes, and the generation thereof is a combined process of kinetic control and structural control, and the size of the catalyst transition metal nanoparticles is properly controlled, and the selection of proper process conditions makes it possible to selectively synthesize the carbon allotropes with high efficiency.
The invention discovers that the high-purity single-walled carbon nano tube can be obtained by adding a little water into the carbon-containing raw material gas and carrying out high-temperature catalytic decomposition on the carbon-containing raw material gas under the action of a catalyst containing transition metals such as iron, cobalt, nickel, molybdenum, tungsten and the like. In contrast, with the dry feed gas without water, the products were amorphous carbon and multi-walled carbon nanotubes with minimal single-walled tube formation under otherwise identical conditions. It was also found in the experiment that if the amount of water added is too large, no carbon product is formed. The amount of water required to form single-walled carbon nanotubes is very small and, by stoichiometric, far insufficient to react the amorphous carbon produced with dry feed gas with water gas ( ) The trace water is removed, which shows that the function of the trace water is to inhibit the amorphous carbon and the multi-walled carbon nano-tube from catalyzingThe agent surface is generated to promote the generation of the single-wall carbon nano tube. This may be associated with the fact that water may undergo hydrolysis reactions with the surface of the transition metal particles and may have a strong interaction with the surface of the catalyst support.
Drawings
FIG. 1(a) is an electron microscopic observation of a reaction product in the absence of water in a carbon-containing raw material gas in example 1;
FIG. 1(b) is an electron microscopic view of the reaction product of example 1 in which water was added to the carbon-containing raw material gas;
FIG. 1(c) is an electron microscopic view of the reaction product of example 2 in which water was added to the carbon-containing raw material gas;
FIG. 1(d) is an electron microscopic view of the reaction product of example 3 in which water was added to the carbon-containing raw material gas;
FIG. 2(a) is an electron microscopic view of the reaction product obtained in example 7 in the absence of water in the carbon-containing raw material gas;
FIG. 2(b) is an electron microscopic view of the reaction product of example 7 in which water was added to the carbon-containing raw material gas;
Detailed Description
The following examples illustrate the significant promoting effect of the present invention on the formation of single-walled carbon nanotubes by adding trace amounts of water.
Example 1:
ammonium molybdate, ferric nitrate, magnesium nitrate and citric acid solution are mixed and evaporated to dryness, and the mixture is roasted in air at 550 ℃ to obtain composite oxide powder with the atomic ratio of Mo to Fe to Mg of 3 to 10 to 100, the composite oxide powder is used as a precursor of a Mo-Fe-MgO catalyst, 100Mg of the composite oxide powder is put into a micro fluidized bed reactor with the diameter of 30mm, 150 ml/min of argon is introduced, the temperature is increased to 1000 ℃, 45 ml/min of methane is introduced, the mixture is cooled to room temperature after reaction for 30 min, a crude product is soaked and washed by hydrochloric acid to remove MgO and most of metals, water washing and drying are carried out to obtain 99Mg of black powder, and a picture 1(a) is observed by an electron microscope, and the product is mainly amorphous carbon and multi-walled. Under the same conditions, water with the partial pressure of 0.67kPa is added into the reaction raw material gasto obtain 52mg of black product, and the product is single-walled carbon nanotubes with high purity and the diameter of 1-3nm, which is known from an electron microscope picture 1(b) and almost no amorphous carbon and multi-walled carbon nanotubes appear.
Example 2:
in the same way as the catalyst and reaction conditions in example 1, water with a partial pressure of 1.4kPa was added to the reaction feed gas to obtain 41mg of black product, which is a single-walled carbon nanotube with high purity and shows very little amorphous carbon and multi-walled carbon nanotube as shown in fig. 1(c) of the electron microscope.
Example 3:
in the same way as the catalyst and reaction conditions in example 1, water with partial pressure of 2.0kPa was added to the reaction raw material gas to obtain 40mg of black product, and as can be seen from the electron microscope image of FIG. 1(d), the product was single-walled carbon nanotubes with high purity, and few amorphous carbon and multi-walled carbon nanotubes appeared.
Example 4:
in the same manner as in example 1, the partial pressure of water added to the reaction feed gas was increased to 3.5kPa, and no carbon product was obtained.
Example 5:
ammonium molybdate, ferric nitrate, magnesium nitrate and citric acid solution are mixed and evaporated to dryness, the mixture is roasted in air at 550 ℃, composite oxide powder with the atomic ratio of Mo, Fe and Mg being 2: 10: 100 is used as a precursor of a W-Fe-MgO catalyst, 100Mg of the composite oxide powder is put into a micro fluidized bed with the diameter of 30mm, 150 ml/min of argon is introduced, the temperature is raised to 1000, 45 ml/min of methane gas is introduced, the mixture is cooled to room temperature after reacting for30 min, a crude product is soaked and washed by hydrochloric acid to remove MgO and most of metals, black powder is obtained by washing and drying, and the product is observed by an electron microscope and mainly comprises amorphous carbon and multi-walled carbon nano tubes. Under the same condition, water with the partial pressure of 1.4kPa is added into the reaction raw material gas to obtain black powder, and the electron microscopic picture shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes exist.
Example 6:
ammonium molybdate, ferric nitrate, magnesium nitrate and citric acid solution are mixed and evaporated to dryness, the mixture is roasted in air at 550 ℃, composite oxide powder with the atomic ratio of Mo, Fe and Mg being 2: 10: 100 is used as a precursor of a W-Fe-MgO catalyst, 100Mg of the composite oxide powder is put into a micro fluidized bed with the diameter of 30mm, 150 ml/min of argon is introduced, the temperature is raised to 850 ℃, 45 ml/min of methane gas is introduced, the mixture is cooled to room temperature after reacting for 30 min, a crude product is soaked and washed by hydrochloric acid to remove MgO and most of metals, black powder is obtained by washing and drying, and the product is observed by an electron microscope and mainly comprises amorphous carbon and multi-walled carbon nano tubes. Under the same condition, water with the partial pressure of 1.4kPa is added into the reaction raw material gas to obtain black powder, and the electron microscopic picture shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes exist.
Example 7:
ammonium tungstate, ferric nitrate, magnesium nitrate and citric acid solution are mixed and evaporated to dryness, the mixture is roasted in air at 550 ℃, composite oxide powder with the atomic ratio of W, Fe and Mg being 4: 15: 100 is used as a precursor of a W-Fe-MgO catalyst, 100Mg of the composite oxide powder is put into a micro fluidized bed with the diameter of 30mm, 150 ml/min of argon is introduced, the temperature is raised to 1000 ℃, 45 ml/min of methane gas is introduced, the mixture is cooled to room temperature after reacting for 30 min, a crude product is soaked and washed by hydrochloric acid to remove MgO and most of metals, and the crude product is washed by water and dried to obtain black powder, and the product is mainly amorphous carbon and multi-walled carbon nano tubes according to an electron microscope picture 2 (a). Under the same conditions, water with the partial pressure of 1.4KPa is added into the raw material gas to obtain black powder, and the electron microscope picture 2(b) shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes are generated.
Example 8:
soaking silica gel in mixed solution of ammonium molybdate and cobalt nitrate, evaporating to dryness, and roasting in air at 550 deg.C for decomposition to obtain MoO3∶Co2O3∶SiO2Taking 100mg of composite oxide powder at a ratio of 5: 100, putting the powder into a quartz boat, putting the quartz boat into a tube furnace with a diameter of 30mm to be used as raw material gas, and reactingObtaining single-wall carbon nano-tube, introducing argon gas of 150 ml/min, heating to 850 deg.C, introducing hydrogen gas of 100 ml/min and ethylene gas of 50 ml/min, reacting for 60 min, cooling to room temperature, acid-washing the crude product with HF to remove SiO2And metal, washing and drying to obtain black powder, and observing by using an electron microscope to obtain theproduct mainly comprising amorphous carbon and multi-wall carbon nano tubes. Under the same condition, water with the partial pressure of 1.0kPa is added into the reaction raw material gas to obtain black powder, and an electron microscopic picture shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes exist.
Example 9:
soaking silica gel in mixed solution of ammonium molybdate and ferric nitrate, evaporating to dryness, and roasting in air at 550 deg.C for decomposition to obtain MoO3∶Fe2O3∶SiO2The composite oxide powder with the ratio of 3: 10: 100 is taken and put into a quartz boat with 100mg, and put into a quartz tube furnace with the diameter of 30mm, argon with the volume of 150 ml/min is introduced, the temperature is raised to 850 ℃, then hydrogen with the volume of 50 ml/min and ethylene with the volume of 60 ml/min are introduced, after reaction for 60 minutes, the mixture is cooled to room temperature, and the crude product is washed by HF acid to remove SiO2And metal, washing and drying to obtain black powder, and observing by using an electron microscope to obtain the product mainly comprising amorphous carbon and multi-wall carbon nano tubes. Under the same condition, water with the partial pressure of 1.0kPa is added into the reaction raw material gas to obtain black powder, and an electron microscopic picture shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes exist.
Example 10:
impregnating alumina with mixed solution of nickel nitrate and ferric nitrate, evaporating to dryness, and roasting at 550 deg.C in air for decomposition to obtain NiO and Fe2O3∶SiO2The composite oxide powder with the ratio of 2: 8: 100 is taken and 100mg is put into a quartz boat,putting into a quartz reaction tube with the diameter of 30mm, introducing 150 ml/min nitrogen, heating to 850 ℃, switching to 100 ml/min hydrogen and 100 ml/min CO gas, reacting for 60 min, cooling to room temperature, washing the crude product with sodium hydroxide and hydrochloric acid to removeRemoving Al2O3And metal, washing and drying to obtain black powder, and observing by using an electron microscope to obtain the product mainly comprising amorphous carbon and multi-wall carbon nano tubes. Under the same condition, water with the partial pressure of 1.0kPa is added into the reaction raw material gas to obtain black powder, and an electron microscopic picture shows that the product is single-wall carbon nano-tubes with high purity and the diameter of 1-3nm, and almost no amorphous carbon and multi-wall carbon nano-tubes exist.
Example 11:
in a vertical quartz reaction tube with a diameter of 40m, 500 ml/min of nitrogen gas is introduced from top to bottom to purge, the temperature is raised to about 950 ℃, about 10 ml/min of normal temperature Fe (CO) with a concentration of about 1 Vol% is introduced5Methane, Fe (CO)5Heating to decompose the iron aerosol particles into iron aerosol particles which float in a reactor, simultaneously introducing 300 ml/min of methane preheated to about 950 ℃, decomposing the methane on the surface of an iron catalyst, and adding about 1 Vol% of water vapor into feed gas to obtain the high-purity single-walled carbon nanotube with the thickness of 1-3 nm. If the raw material gas has no water, the product contains a large amount of amorphous carbon and multi-wall carbon nano tubes under the same conditions.
Example 12:
introducing nitrogen gas of 500 ml/min fromtop to bottom into a vertical quartz reaction tube with the diameter of 40m for purging, heating to about 1050 ℃, introducing methane containing about 1 Vol% of cyclopentadienyl iron at the normal temperature of about 10 ml/min, thermally decomposing the cyclopentadienyl iron into iron aerosol particles, floating in the reactor, simultaneously introducing methane preheated to about 1050 ℃ at 300 ml/min, decomposing the methane on the surface of an iron catalyst, and filtering and collecting the product. When about 0.03 Vol% of water vapor is added into the raw material gas, the high-purity single-walled carbon nanotube with the thickness of 1-3nm is obtained. If the raw material gas has no water, the product contains a large amount of amorphous carbon and multi-wall carbon nano-tubes under the same conditions.
Example 13:
introducing nitrogen gas of 500 ml/min into a vertical quartz reaction tube with the diameter of 40m from top to bottom for purging, heating to about 1050 ℃, introducing hydrogen gas containing about 1 Vol% of iron acetylacetonate at the normal temperature of about 10 ml/min, decomposing and reducing the iron acetylacetonate into iron aerosol particles by heating, floating in a reactor, simultaneously introducing methane preheated to about 1050 ℃ at 500 ml/min, decomposing the methane on the surface of an iron catalyst, and collecting products by filtering. When about 0.05 Vol% of water vapor is added into the raw material gas, the high-purity single-walled carbon nanotube with the thickness of 1-3nm is obtained. If the raw material gas has no water, the product contains a large amount of amorphous carbon and multi-wall carbon nano tubes under the same conditions.
Example 14:
in a vertical quartz reaction tube with the diameter of 40m, 500 ml/min of nitrogen is introduced from top to bottom for purging, the temperature is raised to about 1050 ℃, about l0 ml/min of FeCl with the concentration of about 1 Vol% is introduced at normal temperature3Methane, FeCl3The iron aerosol particles are reduced by thermal decomposition and float in the reactor, and simultaneously methane preheated to about 1050 ℃ by 500 ml/min is introduced, the methane is decomposed on the surface of the iron catalyst, and the product is collected by filtration. When about 0.01 Vol% of water vapor is added into the raw material gas, the high-purity single-walled carbon nanotube with the thickness of 1-3nm is obtained. If the raw material gas has no water, the product contains a large amount of amorphous carbon and multi-wall carbon nano tubes under the same conditions.
Example 15:
in a vertical quartz reaction tube with the diameter of 40m, 500 ml/min of nitrogen is introduced from top to bottom for purging, the temperature is raised to about 800 ℃, about 10 ml/min of normal-temperature FeCl containing about 1Vol percent is introduced3Methane, FeCl3The iron aerosol particles are reduced by thermal decomposition and float in the reactor, and simultaneously methane preheated to about 50 ℃ at 500 ml/min is introduced, the methane is decomposed on the surface of the iron catalyst, and the product is collected by filtration. When about 0.02 Vol% of water vapor is added into the raw material gas, the high-purity single-walled carbon nanotube with the thickness of 1-3nm is obtained. If the raw material gas has no water, the product contains a large amount of amorphous carbon and multi-wall carbon nano tubes under the same conditions.
Claims (10)
1. A method for synthesizing single-walled carbon nanotubes comprises the step of decomposing a carbon-containing raw material gas at high temperature in a reactor under the action of a catalyst containing transition metal or alloy particles thereof, wherein the carbon-containing raw material gas is added with water vapor accounting for 0.01-3% of the volume of the carbon-containing raw material gas.
2. The method of synthesizing single-walled carbon nanotubes of claim 1, wherein the carbon-containing feed gas is selected from molecules containing 1 to 8 carbon atoms, or mixtures thereof.
3. The method of synthesizing single-walled carbon nanotubes of claim 2, wherein the carbon-containing feed gas is methane.
4. The method of synthesizing single-walled carbon nanotubes of claim 3 wherein the carbon-containing feed gas further comprises nitrogen, argon or hydrogen as a diluent gas and a sulfur-containing compound as an adjuvant.
5. The method for synthesizing single-walled carbon nanotubes of claim 1, wherein the reaction temperature of said catalytic decomposition is 600-1200 ℃.
6. The method of synthesizing single-walled carbon nanotubes of claim 1, wherein the transition metal is selected from the group consisting of iron, cobalt, nickel, molybdenum, and tungsten.
7. The method for synthesizing single-walled carbon nanotubes of claim 6, wherein the catalyst is MgO or Al with high specific surface area2O3Or SiO2Or the combination of the two is used as a carrier, and the compound loaded with the transition metal is obtained by heating, decomposing and reducing.
8. The method for synthesizing single-walled carbon nanotubes as claimed in claim 6, wherein the catalyst is obtained by decomposition or reduction of a vapor of a compound of a transition metal by heating in a reactor.
9. The method for synthesizing single-walled carbon nanotubes as claimed in claim 7 or 8, wherein said compound of transition metal is selected from the group consisting of oxides, chlorides, nitrates, sulfates, organic acid salts, carbonyl compounds, cyclopentadienyl compounds and acetylacetone compounds of transition metal.
10. The method for synthesizing single-walled carbon nanotubes of claim 1, wherein the reactor is a fluidized bed reactor, a suspended bed reactor or a fixed bed reactor.
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| CN101378988B (en) * | 2006-02-01 | 2012-04-18 | 大塚化学株式会社 | Process and apparatus for producing carbon nanotube |
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| CN103537293A (en) * | 2012-07-12 | 2014-01-29 | 北京大学 | Catalyst used for preparing single-walled carbon nanotube with chirality selectivity and conductivity selectivity as well as preparation method and application thereof |
| CN104395233A (en) * | 2012-06-22 | 2015-03-04 | 国立大学法人东京大学 | Carbon nanotubes and production method thereof |
| CN106829925A (en) * | 2009-07-17 | 2017-06-13 | 西南纳米科技公司 | Catalyst And Method for preparing multi-walled carbon nano-tubes |
| CN107601458A (en) * | 2017-09-12 | 2018-01-19 | 刘云芳 | A kind of preparation method of single-walled carbon nanotube |
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