KR20220161847A - Catalyst Composition for Preparing Carbon Nanotubes - Google Patents

Abstract

The present invention relates to a catalyst composition comprising several types of catalysts having different catalyst compositions and a method for producing carbon nanotubes using the catalyst composition. When the catalyst composition of the present invention is used, the generation of large aggregates is suppressed during the synthesis of the carbon nanotubes, and thus many carbon nanotubes can be manufactured at a low cost.

Description

Catalyst composition for preparing carbon nanotubes {Catalyst Composition for Preparing Carbon Nanotubes}

The present invention relates to a catalyst composition for preparing carbon nanotubes and a method for preparing carbon nanotubes using the catalyst composition.

Carbon nanomaterials include fullerene, carbon nanotube (CNT), graphene, and graphite nanoplate depending on the shape of the material. It is a macromolecule in which six carbon atoms bonded to three other carbon atoms are hexagonal honeycomb-shaped graphite planes rolled into nanoscale diameters.

Since carbon nanotubes are hollow, they are light, have electrical conductivity as good as copper, have thermal conductivity as good as diamond, and have tensile strength comparable to that of steel. Depending on the rolled form, it is also classified into single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and bundled carbon nanotubes (Rope Carbon Nanotubes).

Recently, research on carbon nanotube synthesis technology capable of synthesizing a large amount of carbon nanotubes at once is actively underway. Among various methods, in the case of thermochemical vapor deposition using a fluidized bed reactor, a large amount of It is particularly preferred in that it can synthesize carbon nanotubes.

However, in this method of manufacturing carbon nanotubes, as the carbon nanotubes grow on the surface of the catalyst, a large amount of the grown carbon nanotubes are entangled and a large aggregate is formed. Therefore, there is a need for research on a method capable of minimizing the amount of aggregates exceeding the standard size.

KR 10-2009-0125368 A

The present invention is to solve the above problems, and to provide a catalyst composition capable of suppressing the formation of aggregates of a certain size or more and a method for producing carbon nanotubes using the same.

The present invention includes N types of supported catalysts having different catalyst compositions, the weight average catalyst composition (active component/support) of the N types of supported catalysts is 0.25 to 0.35, and the maximum catalyst composition among the N types of supported catalysts The difference between the value and the minimum value is 0.05 to 0.25, and N is an integer of 2 or more.

In addition, the present invention is a method for producing carbon nanotubes comprising the steps of filling a fluidized bed reactor with the catalyst composition and carbon nanotubes for a bed, and injecting a carbon source gas into the fluidized bed reactor and synthesizing carbon nanotubes by heating provides

In the case of producing carbon nanotubes using the catalyst composition of the present invention, the generation of agglomerates of a standard size or larger is suppressed, so that more carbon nanotubes can be produced from the same amount of raw material.

Hereinafter, the present invention will be described in more detail.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The term 'carbon nanotube' used in the present invention is a secondary structure formed by assembling units of carbon nanotubes in whole or in part to form a bundle, and the units of carbon nanotubes are nano-sized graphite sheets. It has the shape of a cylinder in diameter and has an sp2 bonding structure. At this time, the characteristics of a conductor or a semiconductor may be exhibited according to the angle and structure of the graphite surface being rolled. The units of carbon nanotubes are single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs), depending on the number of bonds constituting the wall. , multi-walled carbon nanotubes), and the thinner the wall thickness, the lower the resistance.

The carbon nanotubes of the present invention may include any one or two or more of single-walled, double-walled, and multi-walled carbon nanotube units.

catalyst composition

According to one embodiment of the present invention, the present invention includes N types of supported catalysts having different catalyst compositions, the weight average catalyst composition (active component/support) of the N types of supported catalysts is 0.25 to 0.35, and the N The difference between the maximum value and the minimum value of the catalyst composition among supported catalysts of the species is 0.05 to 0.25, and N is an integer of 2 or more.

In the manufacturing process of carbon nanotubes using a fluidized bed reactor, conventionally, it is common to synthesize carbon nanotubes using a catalyst having a single composition. However, in the case of using a catalyst of a single composition as described above, since carbon nanotubes grow from a catalyst having the same activity at the beginning of the reaction, the cohesive force between the same carbon nanotubes interacts and after the final synthesis is completed, a relatively large size There was a problem that the amount of aggregate production was not small.

As a result of research focusing on this point, the inventors of the present invention mixed and used catalysts having different compositions, but the formation of large aggregates was prevented by keeping the difference between the weight average catalyst composition and the maximum and minimum values of the catalyst composition within a specific range. A catalyst composition capable of minimizing and maintaining excellent physical properties of synthesized carbon nanotubes was developed.

Specifically, the catalyst composition of the present invention includes N types of supported catalysts having different catalyst compositions. In the present invention, "catalyst composition" means the molar ratio of the active ingredient to the support in the supported catalyst. For example, in the case of a catalyst prepared by supporting 3 moles of Co on 10 moles of an Al support, the catalyst composition is 0.3. Therefore, the fact that the catalyst composition of the present invention includes N types of supported catalysts having different catalyst compositions means that N types of supported catalysts having different molar ratios of the active component to the support are simultaneously included in the catalyst composition.

On the other hand, the catalyst composition can be measured using ICP OES analysis equipment, and can also be calculated from the ratio of the precursor and the support mixed in the synthesis process. In the case of using ICP OES analysis equipment, it can be measured by applying commonly applied analysis conditions. In addition, when a plurality of metals are used as the active component, the catalyst composition may be calculated based on the combined molar ratio of the corresponding metal components of the plurality of metals.

In the catalyst composition of the present invention, N is an integer of 2 or more, preferably an integer of 2 to 4. A catalyst composition in which N is an integer of 5 or more is difficult to prepare, and does not show an improved effect compared to the case where N is 2 to 4 in terms of suppressing the formation of large aggregates.

In the catalyst composition of the present invention, the weight average catalyst composition (active component/support) of the N types of supported catalysts may be 0.25 to 0.35, preferably 0.28 to 0.32. When the weight average catalyst composition does not fall within the above range, there is a disadvantage in that a small amount of carbon nanotubes is produced compared to the input catalyst because the content of the active component is relatively small, and the weight average catalyst composition exceeds the above range and is excessively large. In this case, physical properties of carbon nanotubes, such as bulk density, may be significantly different from those of conventional carbon nanotubes due to an excessive amount of the active ingredient compared to the support. Meanwhile, the weight average catalyst composition may be calculated by multiplying the catalyst composition of each catalyst by the content percentage of the corresponding catalyst based on the weight of the entire catalyst composition, and then summing all of the N types of catalysts. For example, the weight average catalyst composition of a catalyst composition including 20 wt% of a first catalyst having a catalyst composition of 0.2 and 80 wt% of a second catalyst having a catalyst composition of 0.4 is 0.2*0.2+0.4*0.8=0.36.

In the catalyst composition of the present invention, the difference between the maximum value and the minimum value of the catalyst composition among the N types of supported catalysts may be 0.05 to 0.25, preferably 0.10 to 0.15. If the difference between the maximum and minimum values of the catalyst composition is too large, the uniformity of the overall catalyst composition may be reduced, and the uniformity of the produced carbon nanotubes may also decrease. If the difference between the maximum and minimum values of the catalyst composition is too small, There is no practical benefit of using different N catalysts together.

The catalyst composition of the present invention may be for producing carbon nanotubes, and more specifically, may be for producing multi-walled carbon nanotubes. When the catalyst composition of the present invention is used for manufacturing carbon nanotubes, as described above, the formation of macroaggregates is suppressed, thereby improving the economics of the manufacturing process.

In the catalyst composition of the present invention, the support of the supported catalyst included in the composition may include one or more selected from the group consisting of aluminum, magnesium, calcium, and silicon, and the active component is selected from nickel, cobalt, and iron. It may include one or more that are. In the case of using the supported catalyst including the above-listed supports and active components, carbon nanotubes can be produced at a high speed and have excellent physical properties, and the durability of the catalyst itself is excellent. In the N types of catalysts included in the catalyst composition of the present invention, the support and the active component may be the same or different between the N types of catalysts. However, in order to manufacture carbon nanotubes of uniform quality, it is preferable that the support and active components of the N-type catalyst are the same.

Specifically, the catalyst composition of the present invention may include a first catalyst having a catalyst composition of 0.2 and a second catalyst having a catalyst composition of 0.4 in a weight ratio of 1:1, in which N is 2.

Manufacturing method of carbon nanotube

The present invention provides a method for producing carbon nanotubes using the catalyst composition described above, specifically, the steps of filling the catalyst composition and carbon nanotubes for a bed in a fluidized bed reactor, and injecting a carbon source gas into the fluidized bed reactor Provided is a method for producing carbon nanotubes comprising synthesizing carbon nanotubes by heating.

The catalyst composition used in the production method of the present invention is as described above.

Meanwhile, in the production method of the present invention, the carbon source gas is a carbon-containing gas capable of forming carbon nanotubes by decomposition at a high temperature, and specific examples include various carbon-containing compounds such as aliphatic alkanes, aliphatic alkenes, aliphatic alkynes, and aromatic compounds. Can be used, more specifically, methane, ethane, ethylene, acetylene, ethanol, methanol, acetone, carbon monoxide, propane, butane, benzene, cyclohexane, propylene, butene, isobutene, toluene, xylene, cumene, ethylbenzene , naphthalene, phenanthrene, anthracene, acetylene, formaldehyde, acetaldehyde and the like can be used.

In the manufacturing method of the present invention, a fluidizing gas together with a carbon source gas may be injected into the fluidized bed reactor. The fluidizing gas is for imparting fluidity to the carbon nanotubes and catalyst particles synthesized in the fluidized bed reactor, and a gas having high thermal stability without reacting with the carbon source gas or the carbon nanotubes can be used. For example, nitrogen gas or an inert gas may be used as the fluidizing gas.

Any fluidized bed reactor used in the production method of the present invention may be used without particular limitation as long as it is known to be used for producing carbon nanotubes.

In the production method of the present invention, the heating in the synthesis step may be such that the temperature inside the fluidized bed reactor becomes 600 to 800 ° C. When the temperature in the reactor is within the above-described range, the carbon source gas is easily decomposed and carbon nanotubes can be easily synthesized. If the temperature does not fall within the above-mentioned range, there may be a problem that carbon nanotubes are not well produced, and if the temperature exceeds the above-mentioned range, not only a lot of cost is consumed for heating, but also the catalyst particles themselves are decomposed. this can happen

Hereinafter, examples and experimental examples will be described in more detail to specifically describe the present invention, but the present invention is not limited by these examples and experimental examples. Embodiments according to the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Examples and Comparative Examples - Preparation of Catalyst Compositions

Catalysts having various catalyst composition values were prepared using alumina as a support and cobalt as an active component. Specifically, after preparing an aqueous solution in which the cobalt precursor was dissolved, the aqueous solution was supported on alumina, dried and calcined to prepare the catalyst, and only the amount of cobalt was changed, but the rest of the conditions were the same. . Catalyst compositions of Examples and Comparative Examples were prepared by mixing the prepared catalysts at various weight ratios. In each case, the catalyst composition values and mixing weight ratios of the catalysts mixed are summarized in Table 1 below.

Co/Al of Catalyst 1 Co/Al of Catalyst 2 mixed weight ratio Weight average catalyst composition Difference between maximum and minimum values of catalyst composition Example 1-1 0.36 0.24 1:1 0.3 0.12 Example 1-2 0.36 0.24 1:2 0.27 0.12 Example 1-3 0.36 0.24 2:1 0.33 0.12 Comparative Example 1-1 0.36 0.24 1:14 0.248 0.12 Comparative Example 1-2 0.36 0.24 14:1 0.352 0.12 Example 2-1 0.36 0.24 1:1 0.3 0.12 Example 2-2 0.33 0.27 1:1 0.3 0.06 Example 2-3 0.42 0.18 1:1 0.3 0.24 Comparative Example 2-1 (single catalyst) 0.3 0.3 1:1 0.3 0 Comparative Example 2-2 0.45 0.15 1:1 0.3 0.3

Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2 are for mixing two types of catalysts having the same catalyst composition at different weight ratios, and Examples 1-1 to 1-3 While the silver weight average catalyst composition is included in the range of 0.25 to 0.35, Comparative Examples 1-1 and 1-2 have a weight average catalyst composition of less than 0.25 or greater than 0.35.

In addition, in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2, the two catalysts were mixed at a weight ratio of 1:1, but the catalyst composition of the two catalysts to be mixed was different. In Examples 2-1 to 2-3, the difference between the maximum value and the minimum value of the catalyst composition is included in the range of 0.05 to 0.25, while in Comparative Examples 2-1 and 2-2, the difference between the maximum value and the minimum value of the catalyst composition is less than 0.05 (single catalyst), greater than 0.25.

Experimental Example - Confirmation of physical properties of carbon nanotubes and the amount of aggregates produced

After synthesizing carbon nanotubes using the catalyst compositions prepared in the previous Examples and Comparative Examples, their physical properties were confirmed. A fluidized bed reactor having a diameter of 0.1 m was used, nitrogen gas was introduced at a flow rate of 12 slpm as a fluid gas, and ethylene was introduced at a flow rate of 3 slpm as a carbon source gas. Temperature, reaction time, and catalyst usage in each Example and Comparative Example were applied the same, and after a total of 15 batches were repeated, the average bulk density and purity of the carbon nanotubes for each case were confirmed. The bulk density and purity were measured and calculated through the following methods.

1) Bulk density

After filling the prepared carbon nanotubes in a cup with an internal volume of 50mL by free fall, the weight was measured, and the weight was calculated by dividing the weight by the internal volume of 50mL.

2) Purity

It was calculated as ((sample weight - ash weight) / sample weight)) * 100% using the Ash Test method.

In addition, after 15 reactions were performed for each case, the total amount of carbon nanotubes was recovered, and then aggregates remaining in the reactor were recovered and their weight was measured. In addition to the bottom of the reactor, aggregates attached to the inner wall were also collected, and among the collected aggregates, small aggregates passing through the 2 mm mesh were excluded, and only large aggregates remaining on the mesh were weighed. The results are shown in Table 2 below.

Bulk density (kg/m ³ ) water(%) Aggregate production amount (g) Example 1-1 27.2 95.1 15.3 Example 1-2 27.0 95.0 17.2 Examples 1-3 28.1 95.3 16.8 Comparative Example 1-1 24.2 94.5 30.2 Comparative Example 1-2 31.2 96.0 25.4 Example 2-1 27.2 95.1 15.3 Example 2-2 27.3 95.2 18.2 Example 2-3 27.7 95.0 18.7 Comparative Example 2-1 27.0 95.1 51.0 Comparative Example 2-2 28.1 95.4 45.2

In the case of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2 having different weight average catalyst compositions, compared to carbon nanotubes prepared from the catalyst compositions of Examples satisfying the weight average catalyst composition required by the present invention It was confirmed that the bulk density of the carbon nanotubes prepared from the catalyst composition of Comparative Example was too low or too high. If the bulk density of the carbon nanotubes is too low or too high, it means that the physical properties of the target carbon nanotubes are not implemented, and when the catalyst composition of the comparative example is used, the carbon nanotubes of the desired quality are not obtained. means In addition, it was confirmed that the amount of recovered agglomerates was twice as high as in Example, and when the catalyst compositions of Comparative Examples 1-1 and 1-2 were used, it was confirmed that the yield of the carbon nanotube manufacturing process was lower than that of Example.

On the other hand, in the case of Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2, in which the difference between the maximum and minimum values of the catalyst composition is different, the difference between the maximum and minimum values of the catalyst composition required by the present invention Even in Comparative Examples 2-1 and 2-2, which did not satisfy the range, it was confirmed that the physical properties of the produced carbon nanotubes were similar to those of the carbon nanotubes prepared using the catalyst composition of Example. However, in the case of the amount of aggregates produced, when the catalyst compositions of Comparative Examples 2-1 and 2-2 were used, a very large amount of aggregates were produced compared to the examples, and even compared to Comparative Examples 1-1 and 1-2, a larger amount aggregates were formed. That is, in the case of using the catalyst compositions of Comparative Examples 2-1 and 2-2, a large amount of carbon nanotubes generate aggregates, which means that the economical efficiency of the manufacturing process is greatly reduced.

From the above results, when using the catalyst composition of the present invention, it is possible to produce carbon nanotubes with excellent physical properties, while minimizing the amount of carbon nanotubes lost in the form of aggregates generated during the manufacturing process, thereby efficiently producing carbon nanotubes. It was confirmed that it could be produced.

Claims (7)

It includes N types of supported catalysts having different catalyst compositions,
The weight average catalyst composition (active component / support) of the N types of supported catalysts is 0.25 to 0.35,
The difference between the maximum value and the minimum value of the catalyst composition among the N types of supported catalysts is 0.05 to 0.25,
Catalyst composition, characterized in that the N is an integer of 2 or more.
According to claim 1,
The catalyst composition wherein N is an integer of 2 to 4.
According to claim 1,
The catalyst composition is a catalyst composition for producing carbon nanotubes.
According to claim 1,
The catalyst composition of claim 1, wherein the support of the supported catalyst includes at least one selected from the group consisting of aluminum, magnesium, calcium, and silicon.
According to claim 1,
The catalyst composition according to claim 1, wherein the active component comprises at least one selected from nickel, cobalt and iron.
According to claim 1,
wherein N is 2,
A catalyst composition comprising a first catalyst having a catalyst composition of 0.2 and a second catalyst having a catalyst composition of 0.4 in a weight ratio of 1:1.
Filling a fluidized bed reactor with the catalyst composition according to any one of claims 1 to 6 and carbon nanotubes for a bed; and
A method for producing carbon nanotubes comprising: injecting a carbon source gas into the fluidized bed reactor and synthesizing carbon nanotubes by heating.