JP5193432B2 - Method for producing string-like carbon and method for using the same - Google Patents

Description

The present invention relates to a manufacturing method and use thereof how the string-like carbon, in particular, a gas containing methane as a raw material, relates to the preparation and use thereof how the resulting string-like carbon by chemical vapor deposition .

  In recent years, string-like carbon such as carbon nanotubes has attracted attention as a new material. As methods for synthesizing string-like carbon such as carbon nanotubes, arc discharge methods, laser vapor deposition methods, chemical vapor deposition methods (CVD methods), and the like have been proposed.

In the arc discharge method, a high voltage is applied to two carbon electrodes to cause an arc discharge, thereby generating a multi-layer tube on the deposit (soot) on the cathode side. In the laser deposition method, when carbon mixed with a catalyst is irradiated with strong laser light, the vaporized carbon reacts with the catalyst to obtain single-walled nanotubes. Furthermore, in the CVD method, acetylene or methane, which is a gas containing carbon, and a metal catalyst are chemically reacted at a high temperature to produce carbon nanotubes.
As a method for producing carbon nanotubes by the CVD method, the following Patent Document 1 also discloses a method for producing carbon nanotubes using a catalytic metal selectively formed by forming an insulating layer on a substrate. Yes.
JP 2006-62899 A

Applications of string-like carbon such as carbon nanotubes include application to high-strength materials and conductive resins that utilize properties such as wear resistance, light weight, high strength, and high thermal conductivity, CO ₂ fixation, and nanofilters. To various fields, such as environmental applications such as fuel cells and secondary batteries, biosensors such as biosensors, and electronics such as displays and 10 nm transistors. Is spreading.

  However, in the synthesis method described above, string-like carbon such as carbon nanotubes cannot be produced in a large amount, stably and at low cost, and it has been difficult to use for various purposes.

  On the other hand, in the disposal of waste containing organic matter such as sewage sludge, a large amount of methane gas is generated and reused as gas power generation and automobile fuel in order to increase the energy utilization efficiency. As a result, there are concerns about the impact on global warming.

The problem to be solved by the present invention is to solve the above-mentioned problems and to provide a large amount and a low amount of string-like carbon such as carbon nanotubes, and a method of using the string-like carbon using the characteristics of the string-like carbon Furthermore, it is providing the manufacturing method of the stable string-like carbon.
Also, methane gas discharged from an organic waste treatment facilities such as sewage sludge, which can minimize the impact on global warming, is to provide a method for producing a string-like-carbon.

In order to solve the above-mentioned problem, the invention according to claim 1 is a method for producing string-like carbon, characterized in that chemical vapor deposition is performed at a temperature of 850 ° C. or higher using a gas containing methane as a raw material and limonite as a catalyst. Is the method.
The “string carbon” in the present invention means a carbon composition in which carbon has a three-dimensional crystal structure, such as carbon nanotubes, and grows in a string shape or a tube shape. It means that the composition contains an element other than carbon as long as it does not break down significantly.
In addition, the term “limonite” in the present invention is called limonite or marsh iron ore, which means that produced by the precipitation of water containing a lot of iron such as marshes and shallow seas. Limonite ore (also known as “Aso loess”) collected from the crater lake is listed as preferred.

In the invention which concerns on Claim 2, in the manufacturing method of string-like carbon of Claim 1, this manufacturing method of string-like carbon is integrated in the process of solidifying the methane gas discharged | emitted from an organic waste disposal facility. It is characterized by.

In the invention according to claim 3, produced by the production method of the string-like carbon according to claim 1 or 2, in usage of the string-like carbon, an electromagnetic wave shielding material of the string-like carbon, building materials, paper, adsorbents It is characterized by being used as at least one of the raw materials.

The invention according to claim 4 is the method for using string-like carbon according to claim 3 , wherein the adsorbent is activated carbon used in an organic waste treatment facility.

According to the first aspect of the invention, according to the first aspect of the invention, the production of string-like carbon obtained by chemical vapor deposition at a temperature of 850 ° C. or higher using a gas containing methane as a raw material and using limonite as a catalyst. Because it is a method, there is no need to use a catalytic metal or the like selectively disposed on an insulating layer as in Patent Document 1, and a string-like carbon such as a carbon nanotube is produced stably in large quantities and at a low cost. It becomes possible to do.

According to the invention according to claim 2, since the method for producing string-like carbon is incorporated in the step of solidifying methane gas discharged from the organic waste treatment facility, the methane gas discharged from the organic waste treatment facility is It can be converted into string-like carbon, and global warming can be suppressed, and highly usable string-like carbon can be produced in large quantities and at low cost.

According to the invention according to claim 3 , since the string-like carbon is used as at least one of the raw materials of the electromagnetic shielding material, the building material, the paper, and the adsorbent, the string-like carbon produced in the present invention is used as a magnetic body. It is possible to provide a method of using string-like carbon that takes advantage of the properties and adsorption performance of gas and liquid.

According to the invention of claim 4 , since the adsorbent is activated carbon used in an organic waste treatment facility, it is possible to effectively utilize the excellent adsorptivity of string-like carbon produced in the present invention. Furthermore, since the string-like carbon according to the present invention can be produced even by using methane gas generated in an organic waste treatment facility, a recycling-type organic waste treatment facility that does not produce more waste is provided. Is also possible.

Hereinafter, the present invention will be described in detail using preferred examples.
The method for producing string-like carbon according to the present invention is characterized by performing chemical vapor deposition (CVD) at a temperature of 850 ° C. or higher using a gas containing methane as a raw material and using limonite as a catalyst. In particular, the gas containing methane to be used can be any gas as long as it contains methane and does not contain a gas component that inhibits the production of string-like carbon. In view of this, the gas discharged from the organic waste disposal facility can be used effectively.

Temperature conditions for performing the CVD method, it is necessary to a temperature above 850 ° C. As mentioned above, preferably 1100 ° C. or less, more preferably 9 00 ° C. or higher 1000 ° C. or less.
When the temperature is 800 ° C. or lower, almost no growth of the string-like carbon is observed, and when it exceeds 1100 ° C., energy consumption required for heating becomes enormous, which is not economical and much on the inner wall of the container used for the CVD method. Of carbon may adhere, which is not preferable.
Further, when the temperature is 850 ° C. or higher and 1100 ° C. or lower, the growth of string-like carbon is good, and there is almost no adhesion of carbon to the inner wall of the container. Thus, almost no carbon adheres to the inner wall of the container.

It has been confirmed that the amount of growth of string-like carbon increases in proportion to the synthesis time. For this reason, in order to adjust the length of the string-like carbon, it can be easily controlled only by adjusting the synthesis time.
In addition, even when continuously processing methane gas discharged from an organic waste treatment facility, it is possible to continuously solidify the methane gas by simply supplying methane gas into a container used for the CVD method. Become.

As the ore containing iron oxide used for the production of the string-like carbon of the present invention, any ore can be used as long as it contains iron oxide. In particular, iron oxide is distributed on the surface of the ore. It is preferable from the point that the string-like carbon can be effectively grown, and the string-like carbon grows on the surface of the ore. The surface of the ore includes not only the outer surface but also all surfaces that can be in direct contact with methane gas, for example, those having a porous opening. For example, limonite can be suitably used. The limonite produced at Mt. Aso contains about 70% by mass of Fe ₂ O ₃ and contains an extremely large amount of iron oxide.
Ore containing iron oxide such as limonite can be used in various forms such as powder, granule, pellet, and porous.

The string-like carbon grown on the ore can be used in the grown state, but the string-like carbon can be separated from the ore and used.
In order to separate the string-like carbon from the ore, a method of dissolving the ore component by treating with an acid solution and then filtering, or a method of separating by a magnet after being crushed to an appropriate size can be used. .

The string-like carbon produced in the present invention has magnetism that reacts with a magnet while attached to limonite, and has high gas and liquid adsorptivity and functions as activated carbon.
Needless to say, the string-like carbon can be applied to the fields of high-functional materials, the environment / energy field, the bio / medical field, the electronics field, etc. that have been exemplified as carbon nanotubes. .

In addition to this, by using the conductivity and magnetism of string-like carbon and mixing the string-like carbon into the film body or plate-like body, it can be used as an electromagnetic wave shielding material.
In addition to using the high adsorptive properties of string-like carbon, in addition to using it as an adsorbent, it can be mixed into materials such as building materials and paper, or applied to the surface to create high added value building materials that have adsorptive properties. It is also possible to provide paper.

Next, a technique for incorporating the method for producing string-like carbon of the present invention in an organic waste treatment facility such as a sewage treatment plant will be described with a specific example.
FIG. 1 is a diagram schematically illustrating a treatment flow of a sewage treatment plant.
The sewage is accumulated in the first settling basin 1 and the precipitated sludge-like waste is introduced into the concentration tank 2 by the pump P. In the concentration tank 2, the waste accumulated in the lower layer using gravity is introduced into the sludge storage tank 3 by the pump p.
Moreover, in the gravity concentration tank 2, the deodorizing tower which has arrange | positioned activated carbon is connected, and it is comprised so that the malodorous gas which generate | occur | produces from waste may be filtered and discharged | emitted outside.

In the sludge storage tank 3, surplus concentrated sludge discharged from other processing facilities or other processes is also mixed as necessary. Gases (CH ₄ , CO ₂ , H ₂ S, etc.) discharged from the sludge storage tank 3 are introduced into the desulfurization tower 5 and sulfur components are separated. Further, the organically decomposed solid content collected in the sludge storage tank 3 is sent to the sludge dewatering tank 4 by the pump P, separated from water and discarded.

Gases (CH ₄ , CO _2, etc.) discharged from the desulfurization tower 5 are introduced into a carbide production path 6 for synthesizing string-like carbon, and a boiler 7 for maintaining the carbide production furnace 6 at a predetermined temperature. It is also used as a fuel.
Further, surplus gas from the desulfurization tower 5 can be once introduced into a stored gas tank and accumulated.

The carbide producing furnace 6 is provided with a mineral 8 having an oxide such as limonite, and the temperature inside the furnace is maintained at a temperature exceeding 800 ° C., for example, 900 ° C. by the boiler 7. Gas from the desulfurization tower 5, particularly methane, is introduced into the furnace, and string-like carbon 9 is gradually generated on the surface of the mineral 8 by the CVD method. Thereby, carbon of methane gas will be solidified.
The gas not involved in the reaction in the furnace becomes a clean gas 12 by the filtration filter 10 having the paraffin liquid 11 and is discharged to the outside.

  The string-like carbon 9 synthesized in the carbide making furnace 6 is separated from the mineral 8 as necessary and used as a raw material for various members as described above. Also, in the organic waste treatment facility, for example, string-like carbon or string-like carbon attached to a mineral can be used as activated carbon in a deodorization tower incorporated in the gravity concentration tank 2. According to such a configuration, an organic waste treatment facility with less waste can be configured.

Next, specific examples of the string-like carbon of the present invention will be described.
Example 1
As a mineral containing iron oxide, 0.1 g of limonite (trade name: Aso Kochi Co., Ltd., manufactured by Nihon Limonite Co., Ltd.) (using a powder that has passed through a 50 mesh sieve and further pulverized with a mortar, etc.) Placed in a reaction furnace (capacity: 589 cm ³ , diameter: 5.0 cm × length: 30 cm), maintaining the temperature in the furnace at 900 ° C., introducing methane gas at a flow rate of 30 ml / min, and reacting for 1 hour, on limonite The string-like carbon of Example 1 was obtained by chemical vapor deposition of string-like carbon.
However, the limonite was heat-treated at 600 ° C. for 5 hours in the atmosphere before being treated by the CVD method. Even when such heat-treatment is not carried out, a string-like carbide can be obtained similarly. Have confirmed.

(Example 2)
A string-like carbide of Example 2 was obtained in the same manner as in Example 1 except that the temperature in the furnace was set to 1000 ° C.
(Comparative Example 1)
The process was performed in the same manner as in Example 1 except that the temperature in the furnace was set to 800 ° C., and Comparative Example 1 was obtained.
(Comparative Example 2)
A treatment was performed in the same manner as in Example 1 except that the temperature in the furnace was set to 700 ° C., and Comparative Example 2 was obtained.
(Comparative Example 3)
The process was performed in the same manner as in Example 1 except that the temperature in the furnace was set to 600 ° C., and Comparative Example 3 was obtained.

  Examples 1 and 2 and Comparative Examples 1 to 3 were observed with an electron microscope (product name: S-4000, manufactured by Hitachi, Ltd.). The observation results are shown in FIGS. 2 is a micrograph of Example 1 (magnification 10,000 times), FIG. 3 is a micrograph of Example 2 (magnification 10,000 times), and FIG. 4 is a micrograph of Comparative Example 1 (magnification 10,000 times). FIG. 5 shows a micrograph of Comparative Example 2 (magnification 10,000 times), and FIG. 6 shows a micrograph of Comparative Example 3 (magnification 10,000 times).

  As can be easily understood from the micrographs of FIGS. 2 to 6, string-like carbon is synthesized when the temperature in the furnace is set to 900 ° C. and 1000 ° C. Moreover, although the production | generation of string-like carbon was not able to be confirmed at 800 degreeC, when the temperature in a furnace was set to 850 degreeC and what was processed similarly to Example 1 was observed with the electron microscope, precipitation of carbon was carried out. Observed. From this, carbon precipitates and grows at a temperature where the reaction temperature exceeds 800 ° C., and further, as the synthesis time becomes longer, as described later, the deposition of carbon further proceeds, so the CVD execution temperature exceeds 800 ° C. It is necessary to set the temperature.

Next, in order to examine the influence of the synthesis time on the formation of the string-like carbon, the change in the weight of the carbide when the synthesis time of Example 1 was changed between 1 hour and 9 hours was measured.
As a measurement result, the amount of increase when the weight of the original mineral is normalized to 1 is shown in the graph of FIG.

According to the graph of FIG. 7, after 1 hour has elapsed from the start of synthesis, the weight of the carbide increases in proportion to the synthesis time. It is easily understood that carbon can be solidified.
In addition, after 6 hours or more, the weight of limonite used as a mineral reaches 3 times or more, and it is understood that limonite is a material suitable for carbonization and can promote carbonization very efficiently. Is done.

  Moreover, when the magnet was brought close to the string-like carbon attached to limonite prepared in Example 1, it was attracted to the magnet. From this, it is understood that the string-like carbon attached to the limonite according to the present invention has magnetism. This is considered that the properties of limonite changed to have magnetism in the course of the CVD method rather than the string-like carbon itself having magnetism.

As described above, according to the present invention, it is possible to provide a large amount and a low amount of string-like carbon such as carbon nanotubes, and to provide a method of using the string-like carbon using the characteristics of the string-like carbon, Furthermore, it is possible to provide a stable method for producing string-like carbon.
Also, methane gas discharged from an organic waste treatment facilities such as sewage sludge, which can minimize the impact on global warming, it is possible to provide a manufacturing method of the cord-like-carbon.

It is a figure explaining the processing flow in the case of incorporating the manufacturing method of the string-like carbon of the present invention in an organic waste processing facility. The electron micrograph of Example 1 (reaction temperature 900 degreeC) is shown. The electron micrograph of Example 2 (reaction temperature 1000 degreeC) is shown. The electron micrograph of the comparative example 1 (reaction temperature 800 degreeC) is shown. The electron micrograph of the comparative example 2 (reaction temperature 700 degreeC) is shown. The electron micrograph of the comparative example 3 (reaction temperature 600 degreeC) is shown. It is a graph which shows the synthesis time dependence of the weight change which concerns on carbon solidification.

DESCRIPTION OF SYMBOLS 1 Sedimentation basin 2 Gravity concentration tank 3 Sludge storage tank 4 Sludge dewatering tank 5 Desulfurization tower 6 Carbide preparation furnace 7 Boiler 8 Mineral 9 String carbon 10 Filtration filter 11 Paraffin liquid 12 Exhaust gas

Claims (4)

A method for producing string-like carbon, characterized in that chemical vapor deposition is performed at a temperature of 850 ° C. or more using a gas containing methane as a raw material and limonite as a catalyst.   The string-like carbon production method according to claim 1, wherein the string-like carbon production method is incorporated in a step of solidifying methane gas discharged from an organic waste treatment facility. A method for producing carbon.   The method for using string-like carbon produced by the method for producing string-like carbon according to claim 1 or 2, wherein the string-like carbon is one of at least one of raw materials for electromagnetic shielding material, building material, paper, and adsorbent. A method of using string-like carbon, characterized in that it is used as:   4. The method for using string-like carbon according to claim 3, wherein the adsorbent is activated carbon used in an organic waste treatment facility.

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