KR100980654B1 - Manufacturing method of the catalyst - Google Patents

Abstract

The present invention relates to a catalyst for carbon nanotubes and a method for producing the same, wherein the catalyst for carbon nanotubes according to the present invention is composed of 30% by weight to 70% by weight of iron oxide, 0.01% to 0.3% by weight of sulfur, and the balance thereof. The balance includes a carrier component including silica, magnesia and alumina, and the total content of silica, magnesia and alumina in the carrier component is 80% by weight to 100% by weight. As a result, a catalyst for carbon nanotubes capable of inexpensively mass-producing high purity carbon nanotubes is provided.

Description

MANUFACTURING METHOD OF THE CATALYST}

The present invention relates to a catalyst for producing carbon nanotubes by a gas phase synthesis method and a method for producing the same.

Carbon nanotubes are another form of graphite in which one carbon atom is bonded to three other carbon atoms to form a hexagonal honeycomb structure. Carbon nanotubes have excellent electrical properties, high mechanical strength, and chemically stable materials, so they can be used in a variety of applications in the mechanical and electronic information industries.

Korean Patent No. 2004-0017643 discloses a method for preparing a catalyst to prepare carbon nanotubes, but it requires complex processes such as coprecipitation, drying, pulverization, calcination and sintering, and causes air pollution during production. Phosphorus nitrogen oxides are generated, which is disadvantageous in terms of time and cost.

Accordingly, an object of the present invention is to provide a catalyst for carbon nanotubes and a method for producing the same, which are environmentally friendly and low in manufacturing cost.

The object of the present invention is a catalyst for producing carbon nanotubes, consisting of 30% to 70% by weight of iron oxide, 0.01% to 0.3% by weight of sulfur, and the balance, the balance comprises silica, magnesia and alumina And a carrier component, wherein the total content of silica, magnesia and alumina in the carrier component is solved by 80 to 100% by weight.

In the catalyst for preparing carbon nanotubes, the silica may be 5 wt% to 30 wt%, the magnesia may be 5 wt% to 30 wt%, and the alumina may be 1 wt% to 40 wt%.

The carbon nanotube production catalyst may be a powder having an average diameter of 10 to 50 ㎛.

The object of the present invention is a method for producing a catalyst for producing carbon nanotubes by a gas phase synthesis method, 30% to 70% by weight of iron oxide, 0.01% to 0.3% by weight of sulfur, and the balance, the balance is silica And a carrier component comprising magnesia and alumina, wherein the total content of silica, magnesia and alumina in the carrier component is 80% to 100% by weight; It can be solved by including grinding the mineral.

In the mineral, the silica may be 5% to 30% by weight, the magnesia may be 5% to 30% by weight, and the alumina may be 1% to 40% by weight.

Milling the mineral; The method may further include drying the milled mineral, and the grinding of the mineral may be performed on the dried mineral.

Firing the pulverized mineral; The method may further include milling the calcined mineral.

The regrinding may be performed such that the average diameter of the calcined mineral is 10 μm to 50 μm.

The firing may be performed at 700 ° C. to 1500 ° C. for 1 hour to 8 hours in an oxidizing atmosphere.

According to the present invention, since the catalyst is manufactured using natural minerals, it is suitable for mass production, has low manufacturing cost, and is an environmentally friendly carbon nanotube production catalyst which does not generate any pollutants such as nitrogen and sulfur oxides during catalyst production. The manufacturing method is provided.

The catalyst for producing carbon nanotubes according to the present invention is obtained from natural minerals and consists of iron oxides, sulfur and residual components. The balance component is mostly a carrier component, and the carrier component includes silica, magnesia and alumina. The total content of silica, magnesia and alumina may be 80% to 100% by weight of the carrier component.

Since the catalyst is obtained from the mineral, the residual component is a trace but may include other components such as calcium oxide, manganese, phosphorus, titanium oxide, copper, zinc, potassium oxide, sodium oxide, vanadium and the like. These may be included in 0.001% by weight to 1% by weight based on the entire catalyst for each component.

When the iron oxide component is reduced to hydrogen, it becomes a metal catalyst, and contains 30 wt% to 80 wt%. If the amount of iron oxide used is less than 30% by weight or more than 80% by weight, the activity of the finished catalyst is inferior. Iron oxides include several kinds of oxides different from each other. In the case where ferric oxide is contained in an amount of 50 wt% to 60 wt% in the total catalyst, catalytic activity is high.

Sulfur acts as a promoter to promote the activity of the catalyst. If the sulfur content is lower than 0.01% by weight, there is no role in contributing to catalytic activity. If the sulfur content is higher than 0.3% by weight, sulfur dioxide is generated and adheres to the surface of the catalyst, thereby lowering the activity of the catalyst.

Silica, alumina and magnesia serve as catalyst carriers. Their content may be 80% to 100% by weight in the carrier component. That is, the carrier component of the catalyst according to the present invention mainly consists of silica, alumina and magnesia.

5 wt% to 30 wt% of silica, 5 wt% to 30 wt% of magnesia, and 1 wt% to 40 wt% of alumina may be used throughout the catalyst.

Hereinafter, a method for preparing a carbon nanotube catalyst according to the present invention will be described with reference to FIG. 1.

1 is a flowchart illustrating a method for producing a catalyst of carbon nanotubes according to an embodiment of the present invention.

First prepare a mineral having a desired composition (S100). The mineral comprises 30% to 70% by weight of iron oxide, 0.01% to 0.3% by weight of sulfur and the balance, the balance comprising a carrier component comprising silica, magnesia and alumina, and in the carrier component silica, magnesia and alumina Is 80% by weight to 100% by weight.

Next, the prepared minerals are mixed and crushed (S200).

In detail, this process uses a ball mill to wet the mineral from 24 to 48 hours. By milling, the mineral becomes a powder having an average particle diameter of 10 µm to 50 µm or less. The smaller the particle diameter, the lower the subsequent firing temperature and the higher the interfacial area between the transition metal and the carrier, thereby increasing the catalytic activity. The mineral powder is dried in an electric oven for 12 to 24 hours, and the dried mineral powder is ground again by dry ball milling.

Next, the pulverized mineral powder is fired (S300).

Firing is carried out for 1 hour to 8 hours at a temperature of 700 ℃ to 1500 ℃ in the oxidative atmosphere. The firing temperature is related to the diameter of the particles of the powder, and the smaller the particle diameter, the lower the firing temperature. When the temperature is 1500 ° C or higher, low melting point materials such as iron oxide are melted to form a very dense structure, which is difficult to fracture. When the temperature is lower than 700 ° C, homogenization of the carrier component and iron oxide is insufficient.

The powder becomes grain of calcined tissue, and carbon nanotubes are synthesized in the grain boundary. Therefore, the smaller the particle size of the powder, the wider the grain boundary, the higher the activity for the production of carbon nanotubes.

The catalyst has an important contact strength at the boundary between the transition metal iron and the carrier, and after pulverization, the grain size becomes homogeneous and the bonding strength between the iron component and the carrier component becomes homogeneous, resulting in improved yield and stabilization of product quality. Can be.

After the fired powder mechanically regrind (S400).

It is preferable that the particle diameter at this time is 10 micrometers-50 micrometers. If the particle diameter is 10 μm or less, it may cause a problem of flying off or sticking to the reactor wall when charging into the reactor to manufacture carbon nanotubes. In addition, when the particle diameter is 50 µm or more, there is a problem of lowering the activity of the catalyst.

According to the method for preparing a catalyst described above, natural minerals are used as a catalyst source, and the production process is relatively simple by pulverization, calcination, regrinding, and the like. Therefore, there is no emission of pollutants, manufacturing cost is very low, and mass production is easy.

Hereinafter, the present invention will be described in detail through experimental results. Experiments were carried out on a total of nine catalysts of Examples 1 and 2 and Comparative Examples 1-7.

The catalysts of Examples 1 and 2 were obtained from minerals having a composition of ferric oxide reference content of 61.3 wt%, silica 15.81 wt%, alumina 2.25 wt%, magnesia 17.37 wt%, sulfur 0.02 wt% and the remainder 3.25 wt%. .

The catalyst of Example 1 was prepared through a calcination process, and the catalyst of Example 2 went through only a pulverization process and did not undergo a calcination process. Milling was carried out for 30 hours, drying for 20 hours, and firing for 4 hours at 1000 ° C.

The catalysts of Comparative Examples 1 to 4 were obtained from minerals, and were prepared by similar procedures as in Example. (Comparative Example 1 is a low-grade iron ore, Comparative Examples 2 to 4 are high-grade iron ores having a high iron content. Specifically, Comparative Example 2 is Hamersley Yandi iron ore, and Comparative Example 3 is Hamersley iron ore.)

Comparative Example 1 is a domestic magnetite mineral, and Comparative Examples 2 to 4 are minerals having a high iron content. Specifically, Comparative Example 2 is an Australian iron hydroxide mineral, and Comparative Example 3 is an Australian Hematite mineral.

The catalysts of Comparative Examples 5 to 7 were obtained by mixing, calcining and pulverizing the reagents.

Table 1 shows the composition, firing temperature and source of the catalysts prepared for Examples and Comparative Examples.

TABLE 1

Carbon nanotube synthesis experiment was performed using the catalyst obtained as described above.

The reactor used for the synthesis experiment was a quartz tube with a diameter of 60 mm, the synthesis time was 40 minutes, and ethylene gas and hydrogen gas were used at a ratio of 1:10 as the synthesis gas. The flow rate of ethylene was 0.1 liters per minute and hydrogen was 1 liter per minute. The reaction temperature was 650 ° C, and argon gas was used for the temperature increase and cooling. The catalyst loading was 0.1 g, and the catalyst was synthesized by spreading the catalyst on alumina boats.

Table 2 shows the yield, purity and main product of carbon nanotubes obtained from each catalyst. The yield is the weight ratio of carbon nanotubes to the weight of the charged catalyst.

Figure 2 and Figure 3 are SEM and TEM image of CNT synthesized using the catalyst of Example 1.

TABLE 2

Looking at Example 1 and Example 2 it can be seen that MWCNT (multiwall cabon nano tube) can be obtained in high yield and high purity. The yield and purity of Example 1, which has undergone calcination, are higher than those of Example 2, which shows the improvement of yield and the stabilization of product quality through the homogenization of grain size by the calcination and the homogenization of the competing strengths of the iron component and the carrier component. .

In Comparative Example 1, the main component of the carrier was titanium oxide, in which case carbon nanofibers were produced, and the yield and purity were also lowered. Therefore, it can be seen that the carrier component should be silica, magnesium and alumina as main components.

Comparative Example 2 to Comparative Example 4 was a high purity iron ore was not good yield and purity, because the content of the iron oxide component is too high. In Comparative Example 4, carbon nanofibers were produced in the same manner as in Comparative Example 1.

Comparative Examples 5 to 7 have a low sulfur content, so that the yield and purity are not good. In particular, Comparative Example 5 and Comparative Example 6 is different from the example of the viscosity containing only one carrier component.

1 is a flowchart showing a method for preparing a catalyst according to the present invention,

FIG. 2 is an SEM image of carbon nanotubes prepared using a catalyst according to Example 1 of the present invention.

3 is a TEM image of a carbon nanotube prepared using a catalyst according to Example 2 of the present invention.

Claims (9)

delete delete delete In the method for producing a carbon nanotube catalyst by the gas phase synthesis method, 30 wt% to 70 wt% iron oxide, 0.01 wt% to 0.3 wt% sulfur, and the balance, the balance comprising a carrier component comprising silica, magnesia and alumina, wherein the silica, magnesia in the carrier component And preparing a mineral having a total content of alumina of 80% by weight to 100% by weight; Method for producing a catalyst for carbon nanotubes comprising the step of grinding the mineral. The method of claim 4, wherein The silica in the mineral is 5% to 30% by weight, the magnesia is 5% to 30% by weight, the alumina is a method for producing a catalyst for carbon nanotubes, characterized in that 1% to 40% by weight. The method of claim 4, wherein Milling the mineral; Further drying the milled mineral, Crushing the mineral is a method for producing a catalyst for carbon nanotubes, characterized in that performed on the dried mineral. The method of claim 4, wherein Firing the pulverized mineral; The method for producing a catalyst for carbon nanotubes further comprising the step of regrinding the calcined mineral. The method of claim 7, wherein The regrinding is carried out so that the average diameter of the calcined mineral is 10 ㎛ to 50 ㎛. The method of claim 7, wherein The firing is a method for producing a carbon nanotube catalyst, characterized in that carried out for 1 hour to 8 hours at 700 ℃ to 1500 ℃ in an oxidizing atmosphere

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