KR100450028B1 - Method And Apparatus For Synthesis Of Single-walled Carbon Nanotubes Through Explosion Of Hydrocarbon Compounds - Google Patents

Abstract

The present invention relates to a method for synthesizing single-walled carbon nanotubes by an explosion reaction of a hydrocarbon compound and a device therefor, wherein the gaseous mixture in which a gaseous hydrocarbon compound and 10 to 300% oxygen are mixed in a volume ratio with respect to the hydrocarbon compound in a closed reactor. After mixing 0.5 to 20% by weight of the metal catalyst precursor and 0.05 to 5% by weight of the sulfur precursor based on the weight of the hydrocarbon compound, and comprising the synthesis of single-wall carbon nanotubes by explosion reaction by ignition It is composed of

According to the method and apparatus of the present invention, since exothermic reaction by explosion of hydrocarbon compound and synthesis reaction of carbon nanotubes by heat obtained therefrom are performed simultaneously, single layer carbon nanotubes can be synthesized at a very simple and low cost. Reaction by-products have the advantage of being harmless to the environment, such as carbon dioxide, water and the like, for easy separation of the product.

Description

{Method And Apparatus For Synthesis Of Single-walled Carbon Nanotubes Through Explosion Of Hydrocarbon Compounds}

The present invention relates to a method for synthesizing single layer carbon nanotubes using an explosion of a hydrocarbon compound in a gaseous phase and a liquid phase, and an apparatus therefor.

Single-walled carbon nanotubes are less than 5 nm in diameter and are largely anisotropic in structure, ranging from a few microns to several hundred microns in length. And depending on the diameter has a conductor or semiconductor properties. In addition, it is also mechanically strong (about 100 times of steel), has excellent chemical stability, high thermal conductivity, and hollow characteristics. Such carbon nanotubes are actively applied to electromagnetic shielding, electrodes of electrochemical storage devices (secondary cells, fuel cells or super capacitors), field emission displays, electronic amplifiers, or gas sensors.

However, in order for the application technology of the carbon nanotubes to be practical, high-purity carbon nanotubes should be synthesized in large quantities. Current methods for synthesizing single layer (single-wall) carbon nanotubes include arc discharge, laser, thermal and chemical vapor deposition, which synthesize carbon nanotubes in large quantities instead of high purity. There is a drawback to not doing it. Therefore, there is an urgent need for a method for mass production of single-walled carbon nanotubes by an inexpensive and simple process.

The present invention aims to solve these problems of the prior art and technical problems that have been requested from the past.

That is, it is an object of the present invention to provide a method for synthesizing single layer carbon nanotubes by a simple process of supplying a hydrocarbon compound with oxygen into a reactor and then igniting and exploding. According to the method of the present invention, the heat generated by the explosion due to chemical bonding of the supplied oxygen and some hydrocarbon compounds causes decomposition of the remaining hydrocarbon compounds and metal precursors, and also the formation of nano-sized metal clusters, Thus, single layer carbon nanotubes are synthesized. Therefore, since it is not necessary to set the temperature of the reactor high by applying heat from outside, carbon nanotubes can be synthesized by a simple and inexpensive method.

The present invention also provides a production apparatus capable of carrying out the synthesis of single-walled carbon nanotubes by the explosion reaction of the hydrocarbon compound as described above.

1 is a schematic diagram of a single layer carbon nanotube synthesis apparatus according to one embodiment of the present invention;

2 is an electron micrograph of a single layer carbon nanotube obtained by the synthesis method according to one embodiment of the present invention;

3 is Raman spectroscopy of single-walled carbon nanotubes obtained by the synthesis method according to one embodiment of the present invention.

Description of the main symbols in the drawings

100: synthesizer

200: reaction tube

300: spark plug

400: injection hole

500 outlet

In the present invention for achieving this object, a method for synthesizing single layer carbon nanotubes by explosion reaction of a hydrocarbon compound,

0.5-20% by weight of the metal catalyst precursor and 0.05-5% by weight, based on the weight of the hydrocarbon compound, in a gaseous mixture in which a gaseous hydrocarbon compound and 10 to 300% oxygen are mixed in a volume ratio with respect to the hydrocarbon compound in a closed reactor. And mixing the% sulfur precursor followed by synthesizing the monolayer carbon nanotubes by ignition explosion reaction.

According to the method of the present invention, part of the hydrocarbon compound participates in the exothermic reaction by oxidation with oxidation, and the remaining hydrocarbon compound participates in the synthesis of the single-walled carbon nanotubes by heat by the oxidation reaction. Therefore, since the heat is supplied for synthesizing the carbon nanotubes by the exothermic reaction of itself without additional heat from the outside, the manufacturing process is very simple. In addition, since the reaction dispersion carbon dioxide, water, etc. are present in a gaseous state due to the high temperature of the reactor, it can be easily separated from the carbon nanotubes obtained in the solid phase. Thus, it is possible to produce large quantities of desired single-walled carbon nanotubes at low cost.

The hydrocarbon compound used in the present invention is not particularly limited as long as the hydrocarbon compound is present in a gaseous state under reaction conditions, and preferred examples thereof include methane, ethylene, acetylene, propylene, ethane, propane, butane gas, and the like. These may be used in the form of a compound alone or in the form of a mixture of two or more. In some cases, hydrocarbon compounds present in the liquid phase at room temperature may be used. When such liquid hydrocarbon compounds are used in the method of the present invention, they are supplied to the reactor in a heated state so that they can participate in the reaction in the gas phase or the temperature of the reactor. You can also increase the vaporization slightly. Alternatively, liquid reactants may be sprayed into the reactor so that they are at least in the gas phase during the reaction.

Since oxygen serves to provide heat by reacting with some hydrocarbon compounds, it may be pure oxygen gas or mixed gas containing oxygen (eg air). As described above, the mixing amount of oxygen is preferably 10 to 300% with respect to the volume of the gaseous hydrocarbon compound, and when the mixing amount is too small, it is difficult to cause an explosion reaction or a synthesis reaction of carbon nanotubes due to low calorific value even when an explosion reaction occurs. On the other hand, too much is undesirable because it causes a lot of combustion of hydrocarbon compounds to reduce the amount of carbon required for the synthesis of carbon nanotubes. More preferably, the mixing amount is 50 to 150%, particularly preferably 80 to 120%.

The pressure of the mixed gas (a gaseous hydrocarbon compound and oxygen) is not particularly limited because it depends on the physical properties and the amount of the used hydrocarbon compound, the amount of oxygen, the set temperature of the reactor, etc., due to the threshold condition for the explosion reaction. For example, it may be 1 atm to 20 atm. At too low pressure, the density of the mixed gas decreases, so it is difficult to cause an explosion reaction. At too high pressure, the pressure of the reactor is too high at the time of explosion reaction, and thus an expensive device capable of withstanding such high pressure is required.

As can be seen in the following reaction example, the reaction of the mixed gas is performed by the exothermic reaction caused by the partial combustion of the reactant and the carbon nanotube synthesis reaction. In the following reaction example, 2 moles of acetylene (C ₂ H ₂ ) is used as the hydrocarbon compound in response to 2 moles of oxygen, and the remaining carbon participates in the nanotube synthesis reaction.

(1) 2C ₂ H ₂ + 2O _2- > CO ₂ + 2H ₂ O + 3C (number of carbon remaining)

(2) 2C ₂ H ₂ + 2O _2- > 2CO ₂ + 4H + 2C (number of carbon remaining)

Examples of the metal catalyst precursor used as a catalyst in this reaction include ferrocene, cobaltocene, iron pentacarbonyl, nickel carbonyl, and the like. These may be used in the form of a compound alone or in the form of a mixture of two or more. When using a solid catalyst metal, it is dissolved in benzene, toluene, hexane, etc., which are liquid hydrocarbon compounds, made into a liquid phase, and then vaporized and injected into the reactor. This vaporization method will be described later.

As described above, the addition amount of the metal catalyst precursor is 0.5 to 20% by weight relative to the hydrocarbon compound, and when the amount is 0.5% by weight or less, it is difficult to form the nanotubes due to the lack of the metal catalyst. Is not preferred because is likely to be synthesized. More preferable addition amount is 1 to 15 weight%, Especially preferably, it is 2 to 8 weight%.

The sulfur precursor is known to facilitate the synthesis of single-walled carbon nanotubes, a typical example is thiophene (thiophene). As described above, the amount of sulfur precursor added is 0.05% to 5% by weight relative to the hydrocarbon compound, and when the amount is too small, the addition effect is insignificant, and when the amount is too high, the residual amount after the reaction is increased, resulting in impurities of the carbon nanotubes. It is not desirable because it can be. Particularly preferred addition amount is 0.1% by weight to 1% by weight.

Since the metal catalyst precursor and the sulfur precursor exist in a solid state or a liquid state, it is necessary to change the state of a gaseous state and to put it in a reactor. Examples of such vaporization methods include mixing at the rates described above and then feeding into the reactor through a bubbler (or vaporizer), or by evaporating ultrasonically and flowing with a hydrocarbon compound gas injected into the reactor, into the reactor. Will be supplied.

In the method of the present invention, the temperature in the reactor is increased due to the oxidation of hydrocarbons, but in part, the temperature is raised to 2000 ° C., on average 800 ° C., which is an easy temperature for hydrocarbon decomposition and nanotube synthesis. . Therefore, carbon nanotubes can be synthesized even without installing a separate heat source outside the reactor.

The invention also relates to a device for the synthesis of such single layer carbon nanotubes.

Apparatus for synthesizing single layer carbon nanotubes by the explosion reaction of the present invention for achieving this object,

A supply unit for supplying a reactant gas such as a gaseous hydrocarbon compound and oxygen, a metal catalyst precursor, and a sulfur precursor; A vaporization unit for vaporizing a liquid or solid metal catalyst precursor and a sulfur precursor; A closed reaction part in which an explosion reaction occurs; An ignition unit for igniting and exploding the mixed gas in the reaction unit; And a discharge section for discharging the reaction product.

Therefore, in the synthesis apparatus of the present invention, the mixed gas and the metal catalyst precursor injected into the reaction part are exploded while being ignited by the ignition part in the reaction part to generate single-wall carbon nanotubes, and the by-product carbon dioxide, water, and the like are in a gaseous state. It is discharged to the outside through the furnace outlet.

As described above, the gas phase part that changes the liquid or solid metal catalyst precursor and the sulfur precursor into the gas phase is directly connected to the supply part as a vaporizer, a bubbler, or the like. Therefore, as the gaseous hydrocarbon compound is injected into the reaction part through the supply part, the metal catalyst precursor and sulfur precursor changed into the gas phase by the gaseous part are also introduced into the reaction part through the supply part to participate in the synthesis reaction of the present invention.

The reaction unit may be composed of a double-walled reaction tube having a flow passage through which a synthetic reaction by explosion occurs, and preferably, coolant can circulate. The synthesis reaction by explosion may be preferable because the reaction tube needs to be cooled to the state before the reaction in order to proceed with the reaction of the next cycle after the reaction of one cycle is completed and the subsequent cycle is completed.

The supply part and the discharge part are blocked when the gas mixture or the like is injected into the reaction part to maintain the pressure in the reaction tube at a predetermined level or more. In some cases, the reaction unit may have a structure of a cylinder and a piston to allow a variable control of the pressure. For example, the side of the reaction part where the supply part (or the discharge part) is located has a piston part and has a structure that can move inside the cylinder part, which is the remainder of the reaction part. Move in to increase pressure.

The ignition unit is installed in the reaction unit so that the gas mixture introduced into the reaction unit may explode, and a representative example may include an ignition plug. In some cases, an electric heater, a heating laser, or the like may also be used.

Figure 1 schematically shows the structure of the apparatus 100 for synthesizing single layer carbon nanotubes according to one embodiment of the present invention. Synthesis apparatus 100 is composed of stainless steel.

The reaction part in which the synthesis reaction occurs due to the explosion is a rectangular sealed reaction tube 200 having a cross section, and has a double wall structure in which a flow path 210 through which a cooling water circulates is installed. Cooling water inlet 220 is located on one side of the reaction tube 200 and the cooling water outlet 230 is located on the opposite side, and these inlets and outlets 220 and 230 are connected to the flow path 210.

Spark plugs 300 and 302 which cause explosion of the gas mixture introduced into the reaction tube 200 are installed at the upper center and the lower center of the reaction tube 200. In addition, an inlet 400, which is a supply unit for supplying a gas mixture or the like, is provided on the left side of the reaction tube 200, and an exhaust port 500, which is an outlet for discharging the reaction product, is provided on the right side. A gas phase part (not shown) for changing a liquid or solid metal catalyst precursor and a sulfur precursor into a gaseous phase is directly connected to the injection hole 400.

After the synthesis reaction, water and carbon dioxide are generated in the reaction tube 200 by the oxidation reaction, which is present in the water vapor and gaseous state, and the synthesized carbon nanotubes and the nanoparticles are all present in a small powder state. It can be easily discharged out through the exhaust port 500 by gas supplied from the outside during the process, for example, argon or nitrogen.

The above is one exemplary structure, and various modifications and additional structures are possible within the scope of the present invention.

Hereinafter, the synthesis method of the single-walled carbon nanotubes of the present invention will be described through Examples, but the scope of the present invention is not limited thereto.

EXAMPLE

After exhausting a 500 ml reaction tube made of stainless steel as shown in FIG. 1 to a few mTorr, each 500 ml of oxygen gas and acetylene gas were supplied into the reaction tube through each mass flow controller (MFC) to obtain a pressure of 2 atm. It was made. In the supply sequence of the gas mixture, acetylene gas was first supplied into the reaction tube, followed by oxygen gas. Acetylene gas was supplied into the reaction tube through a bubbler in which iron pentacarbonyl (FeCO ₅ ) as a metal catalyst precursor and thiophene (C ₄ H ₄ S) as a sulfur precursor were mixed in a weight ratio of 10: 1. The gas was injected directly into the reaction tube. The amount of iron pentacarbonyl introduced into the reaction tube was approximately 5 mg and the amount of thiophene was 0.5 mg.

Then, an electrical spark was induced to the spark plug installed in the reaction tube to cause an explosion. After 30 minutes had elapsed, it was confirmed that the temperature of the reaction tube was lowered to 30 ° C., and then exhausted through the exhaust port while nitrogen gas was injected through the injection port. Among the exhausted components, solid reaction products, which are carbon nanotubes, were collected.

Figure 2 discloses a photograph of the collected solid phase reaction products observed by electron microscopy. As can be seen in Figure 2, in addition to the spherical particles, there are linear particles having a long shape, which are bundles of nanotubes with multiple monolayer carbon nanotubes attached thereto.

3 discloses Ramanspectroscopy for the captured solid phase reaction product. In FIG. 3, peaks are seen from 100 to 300 cm ⁻¹ , demonstrating that the solid phase reaction product is a monolayer nanotube.

Those skilled in the art to which the present invention pertains, various applications and modifications are possible within the scope of the present invention based on the above description.

According to the method and apparatus of the present invention, since exothermic reaction by explosion of hydrocarbon compound and synthesis reaction of carbon nanotubes by heat obtained therefrom are performed simultaneously, single layer carbon nanotubes can be synthesized at a very simple and low cost. Reaction by-products have the advantage of being harmless to the environment, such as carbon dioxide, water and the like, for easy separation of the product.

Claims (7)

0.5-20% by weight of the metal catalyst precursor and 0.05-5% by weight, based on the weight of the hydrocarbon compound, in a gaseous mixture in which a gaseous hydrocarbon compound and 10 to 300% oxygen are mixed in a volume ratio with respect to the hydrocarbon compound in a closed reactor. A method of synthesizing single-walled carbon nanotubes, characterized in that by mixing the sulfur precursor of%, by the ignition explosion reaction. The method of claim 1, wherein the hydrocarbon compound is one or a mixture of two or more selected from methane, ethylene, acetylene, propylene, ethane, propane, butane gas and the like; The oxygen is pure oxygen gas or a mixed gas with an inert gas; The metal catalyst precursor is one or a mixture of two or more selected from ferrocene, cobaltocene, iron pentacarbonyl, nickel carbonyl and the like; The sulfur precursor is a method of synthesizing single layer carbon nanotubes, characterized in that thiophene. The method of claim 1, wherein the metal catalyst precursor and the sulfur precursor is mixed with the ratio, and then supplied into the reactor through a bubbler (or vaporizer), or with a hydrocarbon compound gas injected into the reactor after vaporizing by ultrasonication. A method for synthesizing single layer carbon nanotubes, characterized by being fed into a reactor. An apparatus for synthesizing single layer carbon nanotubes by explosion reaction according to claim 1, A supply unit for supplying a reactant gas such as a gaseous hydrocarbon compound and oxygen, a metal catalyst precursor, and a sulfur precursor; A vaporization unit for vaporizing a liquid or solid metal catalyst precursor and a sulfur precursor; A closed reaction part in which an explosion reaction occurs; An ignition unit for igniting and exploding the mixed gas in the reaction unit; And a discharge unit for discharging the reaction product. The apparatus of claim 4, wherein the reaction unit comprises a double-walled reaction tube having a flow passage through which cooling water can be circulated. 6. The side of the reaction part where the supply part (or the discharge part) is located has a piston part and has a structure that can move inside the cylinder part which is the remaining part of the reaction part. Single layer carbon nanotube synthesizing apparatus, characterized in that the structure to increase the pressure by moving in the additional cylinder portion. The apparatus of claim 4, wherein the ignition unit is a spark spark plug, an electric heater, or a heat generating laser.