JP5700983B2 - Method for producing carbon nanotubes using palladium carboxylate - Google Patents

Description

  The present invention relates to a method for producing carbon nanotubes using palladium carboxylate as a catalyst.

  Conventional methods for producing carbon nanotubes (hereinafter sometimes abbreviated as CNT) include an arc discharge method, a laser evaporation method, and a chemical vapor deposition method. Among them, the chemical vapor deposition method (CVD method) is known as an effective manufacturing method for mass production of carbon nanotubes.

  In the CVD method, it is known that carbon nanotubes of various diameters can be synthesized by controlling the catalyst metal diameter, and the catalyst metal diameter is controlled uniformly by using the structure of the carrier. There is a method (for example, Patent Document 1).

  In the CVD method, an organic metal compound such as iron acetate, cobalt acetate, or nickel acetate, which is a catalyst precursor, is dissolved in a solvent, applied to a substrate, lyophilized, and reduced to reduce the catalyst precursor to a catalyst metal. There is a method of using the above as a catalyst for carbon nanotube synthesis (for example, Patent Document 2).

JP 2005-272242 A JP 2006-007213 A

  Carbon nanotubes synthesized by the CVD method have a defect that the crystallinity is inferior to carbon nanotubes synthesized by other methods such as an arc discharge method.

  As described above, the carbon nanotube synthesis method by the CVD method is effective for mass production, but more efficient production is required.

  The catalyst used in the conventional CVD method needs to support a metal catalyst on a carrier for the reasons described above, or it is necessary to apply a metalorganic compound dissolved in a solvent to a substrate and perform a reduction treatment after lyophilization. As a result, the process of preparing the catalyst was complicated.

  When carbon nanotubes were synthesized using methane or acetylene as a carbon source, it was necessary to contact the catalyst metal particles at a relatively high temperature.

  When methane is used as a carbon source in the CVD method, organic substances such as benzene and toluene are precipitated, and the growth amount of the carbon nanotube is deteriorated.

  An object of the present invention is to solve the drawbacks of the prior art in which the process of preparing a catalyst is complicated and to efficiently produce carbon nanotubes with high crystallinity.

  As a result of intensive studies to solve the above problems, the present inventors have found that palladium carboxylate such as palladium acetate, which is easily available, can be used as a catalyst as it is without being supported on a carrier. It came to complete.

The present invention for solving the above-described problems is as follows.
(1) Multi-walled carbon nanotube production method of you and growing a multi-walled carbon nanotubes by contacting a palladium acetate catalyst vaporized carbon-containing compound gaseous at 500 ° C. to 1200 ° C..
( 2 ) While introducing a gaseous carbon-containing compound into a powdery palladium acetate catalyst and scattering the palladium acetate catalyst, the gaseous carbon-containing compound and the palladium acetate catalyst are brought into contact at 500 ° C. to 1200 ° C. to grow multi-walled carbon nanotubes. method for producing a multi-layer carbon nanotube you characterized thereby.

  The carbon nanotube production method of the present invention can be used as a catalyst without supporting palladium carboxylate such as palladium acetate, which is relatively easy to obtain, on a carrier, and carbon nanotubes with high crystallinity can be efficiently used. Can be manufactured.

The schematic diagram which shows the manufacturing method of the carbon nanotube by a fixed bed method. The schematic diagram which shows the manufacturing method of the carbon nanotube by a vapor phase growth method. The schematic diagram which shows the manufacturing method of the carbon nanotube by a solid-phase flow method. 1 is a schematic diagram of a carbon nanotube production apparatus used in Example 1. FIG. 3 is an SEM image of the carbon nanotube obtained in Example 1. FIG. (A) is 1000 times, and (b) is 10,000 times. FIG. 3 is a schematic diagram of a carbon nanotube production apparatus used in Example 2. The Raman spectrum of the carbon nanotube obtained in Example 1.

  The present invention relates to a method for producing multi-walled carbon nanotubes, characterized in that palladium carboxylate which is relatively easily available such as palladium acetate is used as a catalyst without being supported on a carrier.

  In the present invention, palladium carboxylate, preferably 1 to 22 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms, is used as a catalyst. Specific examples of the palladium carboxylate having 1 to 22 carbon atoms include palladium formate, palladium acetate, palladium propionate, palladium butyrate, palladium valerate, palladium caproate, palladium enanthate, palladium caprylate, palladium pelargonate, and caprin. Palladium acid, palladium laurate, palladium myristate, palladium palmitate, palladium margarate, palladium stearate, palladium oleate, palladium linoleate, palladium linolenate, palladium arachidonic acid, palladium docosahexanoate, palladium eicosapentaenoate Palladium acid, palladium malonate, palladium succinate, palladium benzoate, palladium phthalate, palladium isophthalate, para terephthalate Um, palladium salicylate, palladium gallate, palladium melitrate, palladium cinnamate, palladium biruvate, palladium lactate, palladium malate, palladium citrate, palladium fumarate, palladium maleate, palladium aconitate, palladium glutarate, adipine Palladium acid, amino acid palladium, palladium nitrocarboxylate and the like can be mentioned. Of these, palladium acetate is preferred because it is easily available. As the palladium acetate, commercially available products (for example, manufactured by Wako Pure Chemical Industries, Ltd., Kanto Chemical Co., Ltd.) can be used. Alternatively, a used waste palladium catalyst may be dissolved in acetic acid and dried to prepare palladium acetate powder.

  The present invention does not require a step of preparing a catalyst as in the prior art, and powdered palladium carboxylate can be used as it is, so that carbon nanotubes can be produced efficiently.

  Examples of the carbon-containing compound that serves as the carbon source of the carbon nanotube in the present invention include hydrocarbons such as methane, acetylene and ethylene, and alcohols such as ethanol and propanol. However, the carbon-containing compound is not limited to these, and any carbon-containing compound that can grow carbon nanotubes may be used.

  The carbon-containing compound is brought into contact with the palladium carboxylate catalyst at a predetermined temperature as a gas. In particular, when methane, acetylene, or ethylene is used as the carbon-containing compound, it is preferable because carbon nanotubes can be produced at a temperature of about 550 to 650 ° C.

  The carbon nanotube obtained by the present invention has high crystallinity. Furthermore, since the carbon nanotube growth rate is high in the production method of the present invention, long carbon nanotubes can be formed in a shorter time than other production methods. The self-supporting film produced from the carbon nanotube obtained by the present invention has a feature of high conductivity.

  Since the contact between the carbon-containing compound and the palladium carboxylate needs to be performed in an oxygen-free atmosphere, the inside of the reaction furnace is previously replaced with an inert gas such as nitrogen, helium, or argon, and the inside of the reaction furnace is placed in an oxygen-free atmosphere.

  The present invention is characterized in that a carbon nanotube is produced by contacting a gaseous carbon-containing compound and palladium carboxylate at a high temperature. According to an embodiment in which the gaseous carbon-containing compound and palladium carboxylate are brought into contact, (1) fixing Examples include a bed method, (2) a vapor phase growth method, and (3) a solid phase flow method. Below, the manufacturing method of each carbon nanotube is demonstrated.

(1) Fixed bed method By placing solid palladium carboxylate as a catalyst in a high-temperature reactor and supplying a gaseous carbon-containing compound there, the catalyst and the carbon-containing compound are brought into contact with each other, and carbon nanotubes are placed on the catalyst. It is a way to grow.

  The fixed bed method synthesizes CNT from the reaction of immobilized catalyst (palladium carboxylate) and carbon-containing compound gas (methane gas, etc.). It is a method to do.

  In general, in the fixed bed method, an atmospheric pressure CVD apparatus including a heat-resistant reaction tube such as quartz, SiC, or alumina and an electric furnace is used. The heat resistant reaction tube can be either vertical or horizontal. The schematic diagram is shown in FIG.

  In FIG. 1, 1 is a heat-resistant reaction agent such as quartz, and 2 is an electric furnace for heating the heat-resistant reaction agent. Powdered palladium carboxylate 5 is placed in a quartz boat 3. The produced CNTs are indicated by 4.

The procedure is as follows.
(I) A quartz boat carrying palladium carboxylate is inserted into the rear 7 of the heat-resistant reaction tube.
(Ii) An inert gas such as nitrogen or helium is supplied, and the inside of the apparatus is replaced with an inert gas to make an oxygen-free atmosphere.
(Iii) Thereafter, a carbon-containing compound gas is supplied to replace the inside of the apparatus with the carbon-containing compound gas.
(Iv) The temperature inside the apparatus is raised to the reaction temperature.
(V) After reaching the reaction temperature, the CNT is grown on the palladium carboxylate catalyst by reacting for a predetermined time.
(Vi) After the CNT growth, the supply of the carbon-containing compound gas is stopped and the inert gas is supplied again. Then, it cools to room temperature.
(Vii) After cooling, the quartz boat in the apparatus is taken out, and the grown CNTs are taken out.

  The shape of the solid palladium carboxylate used in the fixed bed method may be used as it is, but it may be formed into a film by applying palladium carboxylate dissolved in a solvent on the substrate.

(2) Vapor phase growth method In this method, a vaporized palladium carboxylate catalyst and a gaseous carbon-containing compound are introduced into a high-temperature reaction path, the catalyst and the carbon-containing compound are brought into contact with each other, and carbon nanotubes are grown.

  The vapor phase growth method is a method for synthesizing CNTs from the reaction between a vaporized catalyst (palladium carboxylate) and a gas (methane gas or the like) serving as a carbon source. In general, in the vapor phase growth method, an atmospheric pressure CVD apparatus including a heat-resistant reaction tube such as quartz, SiC, or alumina and an electric furnace is used. The heat resistant reaction tube can be either vertical or horizontal.

  FIG. 2 shows an outline of a reaction apparatus used in the vapor phase growth method. The same elements as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  As the heat-resistant reaction tube, a Y-shaped tube (FIG. 2) or a straight tube (FIG. 5) can be used. When a Y-shaped reaction tube is used, a quartz boat loaded with palladium carboxylate is inserted into one of the two branched reaction tubes at the front, and the other serves as a carbon-containing compound gas supply unit. .

The procedure is as follows.
(I) An inert gas is supplied into the apparatus, and the inside of the apparatus is replaced with an inert gas to create an oxygen-free atmosphere.
(Ii) The temperature in the rear 7 of the reaction tube is raised to the reaction temperature.
(Iii) When a Y-shaped reaction tube is used, the temperature of one branch pipe in the front 8 of the reaction tube provided with a quartz boat carrying palladium carboxylate is raised to a temperature at which palladium carboxylate is vaporized. Meanwhile, the inert gas is continuously supplied. The palladium carboxylate is vaporized by heating and is supplied to the rear 7 of the quartz reaction tube heated to the reaction temperature by supplying an inert gas. A carbon-containing compound gas is supplied from the other branch pipe. In the rear of the reaction tube heated to the reaction temperature, the paradium carboxylic acid gas and the carbon-containing compound gas undergo a gas phase reaction to produce CNTs.

When a straight reaction tube is used, the temperature in front of the reaction tube 8 on which a quartz boat on which palladium carboxylate is placed is set is raised to a temperature at which palladium carboxylate is vaporized while supplying a carbon-containing compound gas. The vaporized palladium carboxylate is supplied to the rear 7 of the reaction tube heated together with the carbon-containing compound gas, and CNTs are generated.
(Iv) After the CNT growth, the supply of the carbon-containing compound gas is stopped and the inert gas is supplied again. Then, it cools to room temperature.
(V) After cooling, CNTs are taken out from the apparatus.

(3) Solid-phase flow method In this method, a carbon-containing gas and a powdery palladium carboxylate catalyst are introduced into a high-temperature reaction path while being scattered, and the catalyst and the carbon-containing compound are brought into contact with each other to grow carbon nanotubes.
The solid-phase flow method is a method of synthesizing CNTs from the reaction of a scattered catalyst (palladium carboxylate) and a gas (methane gas or the like) serving as a carbon source. In general, in the solid phase flow method, an atmospheric pressure CVD apparatus including a heat-resistant reaction tube made of quartz, SiC, alumina or the like and an electric furnace and a solid material supply device (such as a cyclone) are used. The heat resistant reaction tube can be either vertical or horizontal.
FIG. 3 shows an outline of a reaction apparatus used in the solid phase flow method. A difference from FIGS. 1 and 2 is that a solid raw material supply device 6 for supplying the palladium carboxylate catalyst in a dispersed manner is provided on the upstream side of the heat resistant reaction tube 1.
As the solid material supply device, any device such as a cyclone capable of scattering powder can be used.

The procedure is as follows.
(I) Install palladium carboxylate in a solid material feeder.
(Ii) An inert gas is supplied to the solid material supplier, and the inside of the apparatus is replaced with the inert gas.
(Iii) The temperature of the heat-resistant reaction tube is raised to the reaction temperature.
(Iv) By supplying the carbon-containing compound gas from the solid material supply device, the palladium carboxylate powder is scattered in the heat-resistant reaction tube to grow CNTs.
(V) After the CNT growth, the supply of the carbon-containing compound gas is stopped and the inert gas is supplied. Then, it cools to room temperature.
(Vi) After cooling, the CNT in the apparatus is taken out.

Reaction temperature The reaction temperature is 500 to 1200 ° C., preferably 550 to 1000 ° C., more preferably 600 ° C. in any method (fixed bed method, gas phase flow method, solid phase flow method). Perform at ~ 900 ° C. If the temperature is lower than 500 ° C., the carbon-containing compound gas is not decomposed, so that CNT is not generated. If the temperature exceeds 1200 ° C., the carbon-containing compound gas is changed to benzene or toluene, and the efficiency of generating CNT is reduced. Palladium metal of palladium acid acid causes sintering, resulting in a large particle size and difficulty in producing CNTs.

Gas flow rate The faster the gas flow rate, the higher the growth rate, so the faster the flow rate the device can withstand.

About reaction time When using any method (fixed bed method, gas phase flow method, solid phase flow method), the length and amount of CNT increase if the reaction time is long. It is necessary to stop the reaction before the airflow is blocked.

  Palladium carboxylate used as a catalyst in the solid phase flow method needs to be dispersed and reacted, and therefore, a powder having an average particle size of 0.001 to 30 μm, preferably 0.01 to 3 μm is preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1 (fixed floor method)
For the synthesis of CNT, a normal pressure CVD (Chemical Vapor Deposition) apparatus as shown in FIG. 4 was used. The apparatus includes a source gas supply system, a quartz reaction tube 1, an electric furnace 2, and an exhaust system. The diameter of the quartz reaction tube is 50 mm and the length is 900 mm. The electric furnace is a resistance heating furnace having a core portion with a diameter of 50 mm and a length of 600 mm, and temperature control is possible at two locations. Place 1 g of powdered palladium acetate in the quartz boat 3 and install it at the back of the quartz reaction tube (450 mm from the raw material supply side) (measure the weight of the quartz boat and the total weight of the quartz boat and palladium acetate in advance) Keep it.) After installing a quartz boat containing palladium acetate in a quartz reaction tube, nitrogen gas was supplied at 300 sccm (Standard Cubic Centimeter per Minutes), and substitution (oxygen-free state) was performed for 10 minutes. Subsequently, the entire quartz reaction tube was heated to 800 ° C. by an electric furnace. After the quartz reaction tube reached 800 ° C., methane gas was supplied at a flow rate of 2000 sccm, and growth was performed on palladium acetate for 30 minutes. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After opening the electric furnace and cooling to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. It has been found that palladium acetate loses 56% by weight, just to 0.44 g, just before CNT growth. When the amount of CNT growth including the weight loss of palladium acetate was calculated, the CNT grew at about 25 g / 30 minutes. FIG. 5 shows an SEM image of the grown CNT. The grown CNTs had a diameter of 100-300 nm and an average length of 10 μm. The Raman spectrum of the CNT obtained in Example 1 was measured and shown in FIG. As is clear from FIG. 7, since there was no peak at 200 to 600 cm ⁻¹ peculiar to single-walled CNTs, it was estimated that the obtained CNTs were not single-walled.

Example 2 (Vapor phase growth method)
For the synthesis of CNT, the same apparatus as in Example 1 was used. FIG. 6 shows a schematic diagram of the apparatus. 1 g of powdered palladium acetate was placed in a quartz boat and installed in front of the quartz reaction tube (position 150 mm from the raw material supply unit side). After installing a quartz boat containing palladium acetate in a quartz reaction tube, nitrogen gas was supplied at 300 sccm, and replacement was performed for 10 minutes. Thereafter, methane gas serving as a CNT raw material was supplied. Replacement was performed by supplying methane gas at 300 sccm for 10 minutes into the quartz reaction tube. Subsequently, the temperature of the electric furnace was raised. First, the temperature in the rear of the quartz reaction tube was raised to 800 ° C., and then the temperature in the front of the quartz reaction tube was raised to 400 ° C. (temperature increase rate: 25 ° C./1 minute. Palladium acetate begins to vaporize at 248 ° C.). After the temperature in front of the quartz reaction tube reached 400 ° C., the flow rate of methane gas was increased to 2000 sccm, and growth was performed for 30 minutes. Vaporized palladium acetate and methane gas reacted in the rear part of the quartz reaction tube, and CNT grew. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. When the amount of CNT growth was calculated, CNT grew at about 1 g or more / 30 minutes. The grown CNT had a diameter of 50 to 100 nm and a length of 100 μm or more.

Example 3 (solid phase flow method)
A cyclone was used as a solid material feeder. Methane gas was supplied to the palladium acetate powder in the cyclone container to scatter, and CNT growth was performed by supplying it to the same apparatus (fixed bed method) as in Example 1. First, 3 g of palladium acetate powder (98% palladium acetate (II) made by Aldrich) was placed in a cyclone container. Nitrogen gas was supplied at 300 sccm into the cyclone container and the quartz reaction tube, and substitution (oxygen-free state) was performed for 10 minutes. Subsequently, the entire quartz reaction tube was heated to 650 ° C. by an electric furnace (temperature increase rate: 25 ° C./1 minute). Thereafter, 650 sccm of methane gas was supplied to the cyclone container. The scattered palladium acetate powder was supplied to a quartz reaction tube heated to 650 ° C. The growth was performed for 30 minutes. After the growth was completed, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the CNT containing the catalyst in the quartz reaction tube was recovered. The growth amount of CNT was 5 g, the CNT diameter was 10 to 20 nm, and the length was 5 μm or more.

Comparative Example 1
Using the same apparatus as in Example 1, CNT growth using cobalt acetate as a catalyst was performed. First, cobalt acetate tetrahydrate was dried at 120 ° C. for 1 hour for dehydration. 1 g of dehydrated cobalt acetate was placed in a quartz boat and placed behind the quartz reaction tube. After installing a quartz boat containing cobalt acetate in a quartz reaction tube, nitrogen gas was supplied at 300 sccm, and substitution (oxygen-free state) was performed for 10 minutes. Thereafter, methane gas serving as a CNT raw material was supplied. Replacement was performed by supplying methane gas to the quartz reaction tube at 500 sccm for 10 minutes. Subsequently, the entire quartz reaction tube was heated to 650 ° C. by an electric furnace (temperature increase rate: 25 ° C./1 minute). After the quartz reaction tube reached 650 ° C., growth was performed for 30 minutes. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. No increase in weight was confirmed, and CNT was not confirmed even by SEM observation. CNT growth was not confirmed even on cobalt acetate tetrahydrate. From the above results, it was found that CNT growth on cobalt acetate was impossible (CNT growth did not occur because cobalt acetate was decomposed at 200 to 300 ° C., and aggregation of cobalt was remarkably promoted. It seems to be.).

Comparative Example 2
Using the same apparatus as in Example 1, CNT growth using iron acetate as a catalyst was performed. 1 g of iron acetate was placed in a quartz boat and placed behind the quartz reaction tube. After installing a quartz boat containing iron acetate in a quartz reaction tube, nitrogen gas was supplied at 300 sccm, and substitution (oxygen-free state) was performed for 10 minutes. Thereafter, methane gas serving as a CNT raw material was supplied. Replacement was performed by supplying methane gas at 300 sccm for 10 minutes into the quartz reaction tube. Subsequently, the entire quartz reaction tube was heated to 750 ° C. with an electric furnace (temperature increase rate: 25 ° C./1 minute). After the quartz reaction tube reached 750 ° C., growth was performed for 30 minutes. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. No increase in weight was confirmed, and CNT was not confirmed even by SEM observation. The above results indicate that CNT growth on iron acetate is impossible (CNT growth does not occur because iron acetate is decomposed at 200 to 300 ° C., and iron aggregation is remarkably promoted. It seems to be.).

Comparative Example 3
Using the same apparatus as in Example 1, CNT growth using copper acetate as a catalyst was performed. First, copper acetate monohydrate was dried at 120 ° C. for 1 hour for dehydration. 1 g of dehydrated copper acetate was placed in a quartz boat and placed behind the quartz reaction tube. After installing a quartz boat containing copper acetate in a quartz reaction tube, nitrogen gas was supplied at 300 sccm, and substitution (oxygen-free state) was performed for 10 minutes. Thereafter, methane gas serving as a CNT raw material was supplied. Replacement was performed by supplying methane gas to the quartz reaction tube at 500 sccm for 10 minutes. Subsequently, the whole quartz reaction tube was heated to 800 ° C. by an electric furnace (temperature increase rate: 25 ° C./1 minute). After the quartz reaction tube reached 800 ° C., growth was performed for 30 minutes. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube dropped to 550 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. No increase in weight was confirmed, and CNT was not observed even in SEM observation. (The CNT does not grow, probably because copper acetate decomposes at 200 to 300 ° C. and the aggregation of copper is remarkably promoted. .)

Comparative Example 4
Using the same apparatus as in Example 1, CNT growth was performed using a catalyst (Al / Pd = 0.25 / 1) in which palladium acetate was supported on basic aluminum acetate powder. 1 g of palladium acetate / basic aluminum acetate was placed in a quartz boat and placed behind the quartz reaction tube. A quartz boat containing palladium acetate / basic aluminum acetate was placed in a quartz reaction tube, and then nitrogen gas was supplied at 300 sccm to perform replacement (oxygen-free state) for 10 minutes. Thereafter, methane gas serving as a CNT raw material was supplied. Replacement was performed by supplying methane gas at 300 sccm for 10 minutes into the quartz reaction tube. Subsequently, the entire quartz reaction tube was heated to 650 ° C. by an electric furnace (temperature increase rate: 25 ° C./1 minute). After the quartz reaction tube reached 650 ° C., growth was performed for 30 minutes. After 30 minutes, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube dropped to 550 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the quartz boat was taken out and CNTs containing the catalyst were collected. The weight of CNT collected by an electronic balance was measured. A weight increase of 0.4 g was confirmed, and CNT was observed in SEM observation. The observed CNT diameter was 70 to 100 nm and the length was 3 μm (reduction operation seems to be necessary when supported from previous experiments. However, when reduced, palladium acetate itself promotes decomposition. And CNT seems not to grow.)

Comparative Example 5
In the same apparatus as in Example 1, ferrocene (2.5 wt%) / toluene solution was supplied by spray using hydrogen carrier gas to perform CNT growth. First, nitrogen gas was supplied into a spray vaporizer and a quartz reaction tube at 300 sccm, and substitution (oxygen-free state) was performed for 10 minutes. Subsequently, the entire quartz reaction tube was heated to 650 ° C. by an electric furnace (temperature increase rate: 25 ° C./1 minute). Then, 1000 sccm (200-1500 sccm) of hydrogen carrier gas was supplied to the spray vaporizer. A ferrocene (2.5 wt%) / toluene solution dropletized by a spray vaporizer was supplied to a reaction tube heated to 800 ° C. The growth was performed for 30 minutes. After the growth was completed, the supply of the ferrocene (2.5 wt%) / toluene solution to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube was cooled to room temperature, CNT containing the catalyst in the reaction tube was recovered. The weight of CNT collected by an electronic balance was measured. CNT growth inside and outside the quartz reaction tube was not confirmed (CNTs grow when this experiment is performed at 1050 ° C. to 1100 ° C. The toluene used as the CNT raw material is changed to another solvent such as benzene, or a production accelerator. I tried to add thiophene, etc., but the growth temperature could not be lowered.)

Comparative Example 6
The methane was grown by supplying methane gas to the nickel acetate powder in the cyclone container and supplying it to the same apparatus as in Example 1 to perform CNT growth. First, 3 g of nickel acetate powder (average particle size: 3 μm) was placed in a cyclone container. Nitrogen gas was supplied at 300 sccm into the cyclone container and the quartz reaction tube, and substitution (oxygen-free state) was performed for 10 minutes. Subsequently, the entire quartz reaction tube was heated to 850 ° C. (550 ° C. to 800 ° C.) with an electric furnace (temperature increase rate: 25 ° C./1 minute). Thereafter, 1000 sccm (300 to 2000 sccm) of methane gas was supplied to the cyclone container. The scattered nickel acetate powder was supplied to a quartz reaction tube heated to 850 ° C. The growth was performed for 30 minutes. After the growth was completed, the supply of methane gas to the quartz reaction tube was stopped, and 300 sccm of nitrogen gas was supplied. After the temperature of the quartz reaction tube was lowered to 650 ° C., the electric furnace was opened and cooled to room temperature. After the quartz reaction tube cooled to room temperature, the CNT containing the catalyst in the quartz reaction tube was recovered. Black deposits inside and outside the quartz reaction tube were confirmed. SEM observation confirmed that this black deposit was CNT. The growth amount of CNT was 0.5 g, the CNT diameter was 20 nm, and the length was 3 μm or less (compared to the solid-phase flow method of Example 3 using palladium acetate, the CNT production amount was small and the CNT length was also short. .)

  INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it can use palladium carboxylate such as palladium acetate, which is relatively easily available, as a catalyst, and can efficiently produce carbon nanotubes with high crystallinity. .

1 Heat-resistant reaction tube 2 Electric furnace 3 Quartz boat 4 CNT
5 Palladium carboxylate 6 Solid material feeder 7 Rear of reaction tube 8 Front of reaction tube

Claims (2)

Multi-walled carbon nanotube production method you characterized by causing a palladium acetate catalyst vaporized carbon-containing compound gaseous growing multi-walled carbon nanotubes are contacted at 500 ° C. to 1200 ° C.. Introducing a gaseous carbon-containing compound to a powdery palladium acetate catalyst to disperse the palladium acetate catalyst, contacting the gaseous carbon-containing compound and the palladium acetate catalyst at 500 ° C. to 1200 ° C. to grow multi-walled carbon nanotubes method for producing a multi-layer carbon nanotube you characterized.