CN100443403C - Method for continuous synthesis of large-diameter single-walled carbon nanotubes - Google Patents

Abstract

A method for continuously synthesizing large-diameter single-wall carbon nanotubes belongs to the technical field of nanomaterial preparation. The present invention uses transition metal organic compound ferrocene as a catalyst, thiophene as a promoter, methanol or ethanol as a carbon source and a solvent, and an inert gas as a protective gas and a carrier gas to bring the carbon source and the catalyst into the high temperature zone, and the metal organic compound in the high temperature zone The metal iron atoms decomposed by ferrocene are agglomerated in the high temperature area to form nano-iron particles, methanol or ethanol decomposes carbon under the catalysis of high temperature and transition metal iron particles, and form large-diameter single-walled carbon nanotubes, while continuously supplying alcohol and metal Organic ferrocene, the generated single-wall carbon nanotubes are collected in a collector, thereby realizing continuous synthesis of large-diameter single-wall carbon nanotubes. The raw material of the invention is simple and easy to obtain, low in cost, and has no pollution to the environment; inert gas protection is adopted, and there is no obvious flammable dangerous raw material; the product is easy to handle, has high yield, simple equipment, continuous operation, and is suitable for mass production.

Description

Method for continuous synthesis of large-diameter single-walled carbon nanotubes

technical field

The invention relates to a method in the technical field of nanomaterial preparation, in particular to a method for continuously synthesizing large-diameter single-walled carbon nanotubes, that is, using alcohol as a carbon source and thiophene as a growth control agent for floating catalytic continuous synthesis of large-diameter single-walled carbon nanotubes. A method for walled carbon nanotubes (SWCNTs).

Background technique

Depending on the curling angle, SWCNTs have zigzag), armchair and other helical structures. Different helical structures and diameters make SWCNTs have different properties. The discovery of SWCNTs has opened up a new field of vitality for the research of nanoelectronics, nanochemistry, and nanomaterials. In 1997, the discovery and application of SWCNTs was rated as one of the top ten scientific discoveries of the year by the world authoritative magazine Science. The application of SWCNTs is restricted by many factors: large-scale commercial production, purity, agglomeration, and size controllability. At present, there are three main methods for the synthesis of large-diameter SWCNTs: arc method, laser method and chemical vapor deposition method. The electric arc method has simple equipment, but consumes a lot of energy and has a low yield. Laser method equipment is expensive, and the amount of preparation is limited, so it is difficult to promote. The chemical vapor deposition method is divided into two types according to the catalyst introduction method: fixed catalytic cracking method and floating catalytic cracking method. The fixed catalytic cracking method initially disperses catalysts such as iron, cobalt, and nickel on ceramic, silicon, graphite, or glass substrates, and synthesizes SWCNTs on the substrate by catalytic cracking of carbon-containing compounds. The carbon-containing compounds used are usually hydrocarbons or carbon monoxide. This method has a slow synthesis rate and is often accompanied by the formation of multi-walled carbon nanotubes, making it difficult to synthesize in large quantities. As an improvement of the fixed catalyst method, the floating catalytic cracking method is to vaporize the catalyst precursors such as ferrocene and carbonyl iron into the reactor, and directly decompose in the gas phase to form SWCNTs. This method is easy to achieve continuous mass production, but has stricter requirements on the process.

Found through literature search to prior art, Ecole Centrale Paris, LaboratoireMSS/MAT Quang-Hong Yang [Large-Diameter Single-Walled Carbon Nanotubes Synthesized by Chemical Vapor Deposition (chemical vapor deposition method synthetic large-diameter single-walled carbon nanotubes), Adv .Mater. (Advanced Materials) 2003, 15(10), 792. The method of chemical vapor deposition was used to prepare and synthesize large-diameter SWCNTs, but the catalytic decomposition method they adopted, the duration of large-diameter SWCNTs preparation was very short and could only last A few minutes, output is very low, and the collection of product can only be collected in the inner wall of quartz glass tube, can't reach the purpose of large-scale continuous production.

Contents of the invention

The object of the present invention is to address the deficiencies in the prior art, to provide a method for continuously synthesizing large-diameter single-walled carbon nanotubes, using alcohol as a carbon source, thiophene as a growth control agent, and adopting a floating catalytic method to make it directly synthesized at high temperature The carbon and catalyst nanoparticles are decomposed, and the rapid and efficient growth forms high-quality diameter SWCNTs.

The present invention is achieved through the following technical scheme. The present invention uses the transition metal organic compound ferrocene as the catalyst, methanol or ethanol as the carbon source and solvent, and takes the inert gas as the protective gas and carrier gas to quickly bring the carbon source and the catalyst into the high temperature zone In the high-temperature reaction zone, the metal iron atoms decomposed from the metal-organic ferrocene are agglomerated in the high-temperature zone to form nano-iron particles, and methanol or ethanol decomposes carbon under the catalysis of high temperature and transition metal iron particles to form large-diameter SWCNTs. At the same time, since both ethanol and metal-organic ferrocene can be continuously supplied, the generated SWCNTs are collected in the collector, thereby realizing continuous synthesis of large-diameter SWCNTs.

The method of the present invention is further described below, and the method steps are as follows:

(1) The reaction is carried out in a horizontal quartz tube reactor, and an inert gas is introduced, and the temperature is raised to a reaction temperature of 1000-1100° C. at a rate of 20° C./min.

(2) The electronic peristaltic pump is passed into the alcohol solution dissolved with the catalyst, the concentration of the catalyst is 0.5g/300ml-6g/300ml, the concentration of thiophene is 0-9ml/300ml, and the rate of introduction is 0.1-0.8ml/min. The gas flow is adjusted to 80-180l/h, and the catalyst, growth control agent and carbon source are quickly carried into the reaction zone.

(3) The reaction can be carried out continuously, and the reactant is collected by a collector connected to the outlet of the quartz tube. The collected product was refluxed with nitric acid at 120°C for one hour to remove catalyst particles and a small amount of amorphous carbon.

The present invention adopts alcohol as the carbon source, and the transition metal ferrocene as the catalyst and the thiophene of the growth control agent are dissolved in the alcohol and fed in liquid form, and the evaporation rate of the alcohol solution in which the catalyst is dissolved can be adjusted by adjusting the position where the catalyst is introduced. In order to ensure uniform supply, and adjust the carrier gas flow rate to adjust the speed of reactants passing through the high temperature zone, to avoid the decomposed catalyst particles staying in the high temperature zone for too long and grow up, a nozzle can be installed at the outlet of the catalyst to achieve a further homogenization effect. Alcohol and catalyst are supplied at the same time, and carbon and nano-iron particles are decomposed in the high temperature region, directly forming large-diameter SWCNTs. Thus, it solves the long-term and complicated treatment required by the carrier catalyst, and also solves the problem that the catalyst precursor placed at the furnace mouth is easily affected by the temperature of the furnace mouth and the location of the catalyst precursor, and is suitable for continuous production. The process of the present invention is simple and easy, and can conveniently adjust the concentration of the catalyst and the concentration of the thiophene growth control agent to ensure the appropriate ratio of the metal catalyst and carbon according to the difference in the carbon content of the carbon source, so as to control the morphology of the product, and can be used in a wide range Produce high-quality products within the range.

The invention uses alcohol as the carbon source, the raw material is simple and easy to obtain, the cost is low, and there is no pollution to the environment; the inert gas protection is adopted, and there is no obvious flammable and dangerous raw material; the product is easy to handle, the yield is high, the equipment is simple, and continuous operation is possible, suitable for mass production. The average diameter of the obtained SWCNTs is about 5.79nm, and the diameter of the largest single single-walled carbon nanotube is 10.5nm.

Detailed ways

The embodiments of the present invention are described in detail below: this embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are provided, but the protection scope of the present invention is not limited to the following embodiments.

Example 1

The synthesis is carried out in a horizontal quartz reactor. Under the protection of nitrogen gas, the temperature is raised to 1000°C, and the heating rate is 20°C/min, and then the ethanol solution dissolved in ferrocene and thiophene is fed by an electronic peristaltic pump. , the concentration is 0.5g/300ml, the concentration of thiophene is 0, the feeding rate is 0.8ml/min, the flow rate of argon gas is adjusted to 120l/h, and the reaction time lasts for 3 hours. A filmy product was collected at the outlet. The obtained product is a single-wall carbon nanotube bundle, and the diameter of a single single-wall carbon nanotube is about 2 nm. Single-walled carbon nanotubes are relatively pure, with a small amount of metal iron particles adsorbed on the surface.

Example 2

The synthesis is carried out in a horizontal quartz reactor. Under the protection of argon, the temperature is raised to 1100°C, the heating rate is 20°C/min, and then the methanol dissolved with ferrocene and thiophene is fed by an electronic peristaltic pump Solution, the concentration of ferrocene is 4g/300ml, the concentration of thiophene is 3ml/300ml, the feeding rate is 0.5ml/min, the flow rate of argon gas is adjusted to be 180l/h, and the reaction time lasts for 3 hours. A filmy product was collected at the outlet. The original product was treated in nitric acid at 120°C for one hour, washed and dried to obtain a purified product. The average diameter of the obtained SWCNTs is about 5.79nm, the diameter of the largest single SWCNTs is 10.5nm, the phenomenon of bunching is reduced, and more SWCNTs appear in the form of single roots. Statistical data analysis showed that the proportion of 4-9.5nm large-diameter SWCNTs reached 78%.

Example 3

Under argon protection, heat up to 1100°C at a rate of 20°C/min, and then use an electronic peristaltic pump to pass through an ethanol solution dissolved with ferrocene and thiophene. The concentration of ferrocene is 6g/300ml, and the concentration of thiophene is 3ml/300ml, the feeding rate is 0.1ml/min, the argon flow rate is adjusted to 160l/h, and the reaction lasts for 2 hours. Film-like products are collected at the outlet, and the obtained products contain iron nanoparticles, single single-wall carbon nanotubes, single-wall carbon nanotube bundles and a small amount of multi-wall carbon nanotubes. The average diameter of SWCNTs is around 5nm.

Example 4

Under the protection of nitrogen, heat up to 1050°C at a rate of 20°C/min, and then use an electronic peristaltic pump to pass through the methanol solution dissolved with ferrocene and thiophene. The concentration of ferrocene is 4g/1000ml, and the concentration of thiophene is 9ml. /300ml, the feeding rate is 0.6ml/min, the nitrogen flow rate is adjusted to be 160l/h, and the reaction duration is 3 hours. The product collected at the outlet is in the form of a film with strong adsorption. The obtained products are single SWCNTs and SWCNTs tube bundles. The average diameter of SWCNTs is about 4.5nm.

Claims (4)

1; a kind of method of continuously synthesizing large diameter single wall carbon nano-tube; it is characterized in that: use the transition metal organics ferrocene as catalyzer; thiophene is a promotor; methyl alcohol or ethanol are as carbon source and solvent; with the rare gas element is that shielding gas and carrier gas are brought carbon source and catalyzer into high-temperature zone; reunion forms nano iron particles to the metallic iron atom that decomposites at high-temperature zone metallorganics ferrocene in the high-temperature zone; methyl alcohol or ethanol decomposite carbon under the katalysis of high temperature and transition metal iron particle; form large diameter single wall carbon nano-tube; supply with pure and mild ferrocene simultaneously continuously; the Single Walled Carbon Nanotube that generates is collected in collector; thereby realize the serialization synthesizing large diameter single wall carbon nano-tube; described high-temperature zone, its temperature are 1000-1100 ℃.

2, the method for continuously synthesizing large diameter single wall carbon nano-tube according to claim 1 is characterized in that, step is as follows:

(1) is reflected in the horizontal quartz tube reactor and carries out, feed argon gas or nitrogen, be warmed up to temperature of reaction 1000-1100 ℃ with the speed of 20 ℃/min;

(2) feed methyl alcohol or the ethanolic soln that is dissolved with ferrocene and thiophene by electronic peristaltic pump, ferrocene concentration is 0.5g/300ml-6g/300ml, thiophene concentration is 0-9ml/300ml, regulates carrier gas flux to 80-180l/h, carries catalyzer, growth control agent and carbon source rapidly and enters reaction zone;

(3) reaction continues to carry out, and reactant is collected by the collector that links to each other with the silica tube outlet, and the product of collecting refluxes with nitric acid, removes wherein granules of catalyst and a spot of decolorizing carbon.

3, the method for continuously synthesizing large diameter single wall carbon nano-tube according to claim 2 is characterized in that, and is described with the nitric acid backflow, is meant: refluxed one hour at 120 ℃ with nitric acid.

4, the method for continuously synthesizing large diameter single wall carbon nano-tube according to claim 2 is characterized in that, feeds methyl alcohol or the ethanolic soln that is dissolved with ferrocene and thiophene by electronic peristaltic pump, and feeding speed is 0.1-0.8ml/min.