Supported catalysts for producing carbon nanotubes

Abstract

The present invention relates to a supported catalyst for producing carbon nanotubes, comprising a number average particle size (D MN ) is a carrier with a diameter of 1.5 μm to 20 μm and an active component supported in the carrier, wherein the active component that prevents aggregation between particles and supports the particles can serve as an active component, thereby providing a supported catalyst with excellent activity, thereby improving productivity.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0173605 filed on December 11, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0004] The present invention relates to a supported catalyst for preparing carbon nanotubes and a method for preparing carbon nanotubes using the supported catalyst. Background Art

[0005] Carbon nanomaterials can be classified into fullerenes, carbon nanotubes (CNTs), graphene, graphite nanoplates, etc. according to their shapes. Among them, carbon nanotubes are macromolecules in which the surface of hexagonal honeycomb graphite, in which one carbon atom is bonded to three other carbon atoms, is rolled into a nanometer-sized diameter.

[0006] Carbon nanotubes are hollow and therefore lightweight. They also conduct electricity as well as copper, conduct heat as well as diamond, and have the same tensile strength as steel. Depending on their rolled shape, carbon nanotubes can be categorized as single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and rope-shaped carbon nanotubes.

[0007] In recent years, research on carbon nanotube synthesis technology capable of synthesizing a large amount of carbon nanotubes at one time has been actively conducted, and among various methods, thermal chemical vapor deposition using a fluidized bed reactor is favored because it can easily and continuously synthesize a large amount of carbon nanotubes.

[0008] In the synthesis of such carbon nanotubes, the yield of produced carbon nanotubes relative to the amount of catalyst used is increased to reduce production costs and improve productivity. Therefore, increasing the amount of active components supported on a support to increase catalyst activity is commonly employed. However, when the amount of active component supported is increased, a problem arises in that sintering occurs between the active components during the production of the supported catalyst, resulting in reduced catalyst activity when a predetermined amount or more of the active component is supported.

[0009] Therefore, additional research is needed on supported catalysts for producing carbon nanotubes so that the supported catalysts can maximize the production efficiency of carbon nanotubes by optimizing the loading amount of active components.

[0010] Prior art literature

[0011] (Patent Document 1) KR 10-2010-0074002A Summary of the Invention

[0012] Technical issues

[0013] One aspect of the present invention provides a supported catalyst for producing carbon nanotubes, which can improve the synthesis yield of carbon nanotubes by maximizing the loading amount of active components while optimizing the loading efficiency of the active components.

[0014] Technical Solution

[0015] According to one aspect of the present invention, a supported catalyst for producing carbon nanotubes is provided.

[0016] (1) The present invention provides a supported catalyst for producing carbon nanotubes, wherein the catalyst comprises a number average particle size (D MN ) is a carrier with a diameter of 1.5 μm to 20 μm, and an active component loaded in the carrier.

[0017] (2) In (1), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the number average particle size of the support is 4.0 μm to 20 μm.

[0018] (3) In (1) or (2), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the number average particle size of the support is 4.0 μm to 19 μm.

[0019] (4) In any one of (1) to (3), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the content of the active component is 5 wt% to 30 wt% based on the total weight of the supported catalyst for producing carbon nanotubes.

[0020] (5) In any one of (1) to (4), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the active components include a main catalyst component and a co-catalyst component, and the molar ratio of the main catalyst component to the co-catalyst component is 10:0.1 to 10:10.

[0021] (6) In any one of (1) to (5), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the main catalyst component is one or more selected from nickel, cobalt and iron.

[0022] (7) In any one of (1) to (6), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the co-catalyst component is one or more selected from molybdenum and vanadium.

[0023] (8) In any one of (1) to (7), the present invention provides a supported catalyst for producing carbon nanotubes, wherein the supported catalyst is used to produce bundle-type carbon nanotubes.

[0024] (9) The present invention provides a method for producing carbon nanotubes, which comprises injecting the supported catalyst for producing carbon nanotubes of any one of (1) to (8) into a fluidized bed reactor, and supplying a carbon source gas and a flowing gas to the fluidized bed reactor, and then reacting the carbon source gas and the flowing gas to produce carbon nanotubes.

[0025] (10) In (9), the present invention provides a method for producing carbon nanotubes, wherein the carbon nanotubes are bundle-type carbon nanotubes.

[0026] Beneficial effects

[0027] The supported catalyst for producing carbon nanotubes of the present invention has excellent catalytic activity because the loading amount of the active component is optimized according to the selection of the carrier, thereby increasing the effective amount of the active component and, therefore, increasing the yield of the produced carbon nanotubes relative to the input amount of the catalyst. DETAILED DESCRIPTION

[0028] Hereinafter, the present invention will be described in more detail.

[0029] It should be understood that the words or terms used in the description and claims of the present invention should not be interpreted as having only the meanings defined in commonly used dictionaries. It will be further understood that, based on the principle that the inventor can appropriately define the meaning of a word or term to best explain the invention, the word or term should be interpreted as having a meaning consistent with its meaning in the context of the relevant technology and the technical concept of the present invention.

[0030] The term "carbon nanotube" used in the present invention refers to a secondary structure in which carbon nanotube units are assembled to form a bundle in whole or in part, and the carbon nanotube units have a cylindrical graphite surface with a nanometer-sized diameter and an sp2 bonding structure. At this time, depending on the angle and structure of the graphite sheet, it may exhibit conductive or semiconducting properties. Depending on the number of bonds forming the wall, carbon nanotube units can be divided into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs), and the thinner the wall, the lower the resistance.

[0031] The carbon nanotubes of the present invention may include one or more of single-walled carbon nanotube units, double-walled carbon nanotube units, and multi-walled carbon nanotube units.

[0032] Supported catalysts for producing carbon nanotubes

[0033] According to an embodiment of the present invention, there is provided a supported catalyst for producing carbon nanotubes, the catalyst comprising: a number average particle size (D MN ) is a carrier with a diameter of 1.5 μm to 20 μm; and an active component loaded in the carrier.

[0034] The supported catalyst of the present invention selects a carrier with a specific particle size, thereby increasing the effective amount of the supported active component. Therefore, the amount of carbon nanotubes produced can be significantly increased relative to the amount of the catalyst used.

[0035] The supported catalyst for producing carbon nanotubes according to an embodiment of the present invention is particularly suitable for producing bundle-type carbon nanotubes. Bundle-type carbon nanotubes refer to carbon nanotubes having a secondary shape in the form of a bundle or rope, wherein a plurality of carbon nanotubes are arranged or aligned in parallel along a predetermined direction. Compared with tangled carbon nanotubes having a secondary shape of a sphere or potato shape in which a plurality of carbon nanotubes are entangled together in a non-directional manner, bundle-type carbon nanotubes have high dispersibility in a solvent and are therefore suitable for production in a dispersed form. When the supported catalyst for producing carbon nanotubes of the present invention is used, bundle-type carbon nanotubes can be more easily prepared.

[0036] Hereinafter, the supported catalyst according to an embodiment of the present invention will be described in more detail.

[0037] carrier

[0038] The number average particle size (D MN ) is 1.5 μm to 20 μm. When a carrier having a particle size within the above range is used, aggregation between particles of a supported catalyst in which an active component is supported can be prevented, and the effective loading amount of the active component can be maximized.

[0039] Specifically, the number average particle size of the carrier can be 1.5 μm to 20 μm, preferably 4.0 μm to 20 μm, and more preferably 4.0 μm to 19.0 μm. When the number average particle size of the carrier is less than 1.5 μm, the particles of the supported catalyst aggregate due to the cohesive force between them. When the number average particle size of the carrier is greater than 20 μm, the effective amount of the active component no longer increases, so there may be a loss of metal used as the active component. Moreover, the unevenness of the active component supported on the carrier may increase production costs and reduce productivity. Since the particle size distribution is more finely controlled within the above preferred range, the effective amount of the active component supported on the carrier can be further increased.

[0040] The particle size distribution properties of the support can be directly reflected in the supported catalyst used to produce carbon nanotubes, and a supported catalyst having such a particle size distribution can play a significant role in improving the productivity of carbon nanotubes.

[0041] The support may include one or more selected from the group consisting of magnesium oxide, calcium oxide, aluminum hydroxide, zirconium oxide, and silicon oxide, preferably aluminum hydroxide, and more preferably aluminum hydroxide and one or more oxides selected from the group consisting of zirconium oxide, magnesium oxide, and silicon oxide. When using the above-mentioned type of support, there are advantages in that the support has excellent durability and can easily support the active component.

[0042] The shape of the carrier is not particularly limited, but may be spherical or potato-shaped. In addition, the carrier may have a porous structure, a molecular sieve structure, a honeycomb structure, etc., to have a relatively high surface area per unit mass or unit volume.

[0043] Active ingredient

[0044] In the supported catalyst for producing carbon nanotubes according to an embodiment of the present invention, an active component is supported in a carrier, and the active component may include a main catalyst component and a co-catalyst component.

[0045] The main catalyst component may be one or more selected from nickel, cobalt, and iron, with cobalt being particularly preferred. The main catalyst component directly reduces the activation energy of the reaction for synthesizing carbon nanotubes from a carbon source gas, thereby promoting the carbon nanotube synthesis reaction. When the main catalyst component of the above type is used, it is preferred that the catalyst to be prepared has high activity while also ensuring a certain level or higher of durability.

[0046] The co-catalyst component may be one or more selected from molybdenum and vanadium, with vanadium being particularly preferred. The co-catalyst component is used to further enhance the catalytic activity of the main catalyst component. When the co-catalyst component is used, it can have an excellent synergistic effect with the main catalyst component and can prevent agglomeration between the main catalyst components during the manufacturing process.

[0047] According to an embodiment of the present invention, the catalyst component in the supported catalyst for producing the carbon nanotubes of the present invention may have a composition of Formula 1 below.

[0048] [Formula 1]

[0049] (Ni,Co,Fe) x (Mo,V) y

[0050] In the above formula, x is the molar ratio of the main catalyst component, y is the molar ratio of the co-catalyst component, and x and y are real numbers within the range of 1≤x≤10 and 0.1≤y≤10, respectively.

[0051] Specifically, the molar ratio of the main catalyst component to the co-catalyst component may be 10:0.1 to 10:10, preferably 10:0.5 to 10:5. When the composition of the active component is controlled to have such a molar ratio, it is possible to uniformly load the active component in the carrier without agglomeration while maintaining the activity of the supported catalyst at an excellent level.

[0052] According to one embodiment of the present invention, the active component content of the supported catalyst may be 5% to 30% by weight, preferably 10% to 30% by weight, and more preferably 15% to 30% by weight, based on the total weight of the supported catalyst. The active component content here may refer to an effective amount of the catalyst component that substantially participates in carbon nanotube synthesis. To achieve this effective amount, a support having the aforementioned particle size distribution, i.e., a number average particle size and a volume average particle size within a specific range, must be used.

[0053] Preparation method of supported catalyst for producing carbon nanotubes

[0054] The present invention provides a method for preparing the above-mentioned supported catalyst for producing carbon nanotubes. Specifically, the present invention provides a method for preparing a supported catalyst for producing carbon nanotubes, wherein the method comprises: MN The catalyst solution is loaded on a carrier having a particle size of 1.5 to 20 μm, and the mixture is then fired at a temperature of 500 to 800° C. to prepare a supported catalyst.

[0055] As described above, the number average particle size (D MN ) is 1.5 μm to 20 μm, and a carrier satisfying the above number average particle size range can be obtained and used, or can be directly prepared and used. In particular, the obtained or prepared carrier is classified according to its particle size by a classifier, and then only the carrier satisfying the number average particle size within the above range can be taken out and used.

[0056] When the support is directly prepared, the support can be prepared by heat-treating aluminum hydroxide. Furthermore, before performing the heat treatment step, a pretreatment step of aluminum hydroxide (Al(OH)3) can be performed. The pretreatment can be performed at 50°C to 150°C for 1 to 24 hours. When performing the pretreatment, any remaining solvent or impurities that may be present on the surface of the aluminum hydroxide (Al(OH)3) can be removed.

[0057] The porosity of aluminum hydroxide (Al(OH)3) is 0.1 cm 3 / g to 1.0cm 3 / g, and the specific surface area is less than 1m 2 / g.

[0058] By performing the heat treatment, aluminum hydroxide is converted, thereby producing a support containing 30% by weight or more of AlO(OH) and 70% by weight or less of Al(OH)3, specifically 40% by weight or more of AlO(OH)3 and 60% by weight or less of Al(OH)3, but no Al2O3. At temperatures below these temperatures, aluminum hydroxide is not converted to AlO(OH), while at temperatures above these temperatures, aluminum hydroxide is converted, potentially producing Al2O3. The heat treatment can be performed in an air atmosphere. The heat treatment step can be performed at 250°C to 500°C, more specifically 400°C to 500°C.

[0059] In the method for preparing a supported catalyst for producing carbon nanotubes of the present invention, the catalyst solution may be a mixture comprising a main catalyst precursor, a co-catalyst precursor and an organic acid.

[0060] Catalyst solution comprises the precursor of the main catalyst component by load and the precursor of promotor component, and also comprises organic acid.The organic acid used in the present invention can be for example polycarboxylic acid, and it is the compound containing one or more carboxyl groups, and has high solubility, suppresses precipitation and promotes the synthesis of catalyst as complexing agent, and increases the synthesis of carbon nanotube as activator.Polycarboxylic acid can be one or more that are selected from dicarboxylic acid, tricarboxylic acid and tetracarboxylic acid, and can be for example citric acid, oxalic acid, malonic acid, succinic acid, tartaric acid etc.

[0061] The organic acid may be present in an amount of 0.1 to 1.5 wt % based on the total weight of the catalyst solution. Within this range, metal components of the main catalyst and the co-catalyst will not precipitate in the catalyst solution, and cracking during subsequent firing may be suppressed.

[0062] In addition, the sum of the main catalyst precursor and the co-catalyst precursor and the organic acid may be appropriately mixed within a molar ratio range of about 5:1 to 30:1, and when the above molar ratio is satisfied, the bulk density of the prepared carbon nanotubes may be achieved at an excellent level.

[0063] The main catalyst precursor and the co-catalyst precursor can be used without particular limitation, as long as the main catalyst precursor and the co-catalyst precursor are compounds that can be converted into the main catalyst component and the co-catalyst component, respectively, by the following drying and firing processes. In the case of nickel, iron and cobalt as examples of the above-mentioned preferred main catalyst components, any salt or oxide of these metal components, or a compound containing these metal components can be used as the main catalyst precursor, more specifically, materials such as Fe(NO3)2·6H2O, Fe(NO3)2·9H2O, Fe(NO3)3, Fe(OAc)2, Ni(NO3)2·6H2O, Co(NO3)2·6H2O, Co2(CO)8, [Co2(CO)6(t-BuC=CH)], Co(OAc)2, etc. can be used as the main catalyst precursor. In the case of molybdenum and vanadium as examples of the above-mentioned preferred co-catalyst components, any salt or oxide of these components, or a compound containing these components can be used as the co-catalyst precursor, more specifically, materials such as NH4VO3, (NH4)6Mo7O 24 4H2O, Mo(CO)6, (NH4)MoS4 and other materials can be used as co-catalyst precursors. When the above-mentioned materials are used as precursors, the main catalyst component and the co-catalyst component can be smoothly supported.

[0064] The solvent of the catalyst solution is not particularly limited as long as it can dissolve the above-mentioned main catalyst precursor and co-catalyst precursor, and water, for example, is preferably used.

[0065] In the method for preparing a supported catalyst for producing carbon nanotubes of the present invention, after uniformly mixing the support and catalyst solution and before firing the mixture, the loading process may further include an aging process for a predetermined time. Mixing may be performed at a temperature of 45°C to 80°C with rotation or stirring. Aging may be performed for 3 to 60 minutes.

[0066] When the catalyst solution is supported on a carrier, a drying process may be further included before firing. Drying may be performed at 60°C to 200°C for 4 to 16 hours, and typical drying methods used in the art, such as oven drying, vacuum drying, freeze drying, etc., may be used as the drying method.

[0067] The intermediate prepared through the above series of processes is used as a supported catalyst and is fired to produce carbon nanotubes through the following firing step. The firing can be performed at a temperature of 500°C to 800°C, preferably 600°C to 800°C. When fired within this temperature range, most of the main catalyst precursor and the co-catalyst precursor can be converted into the main catalyst component and the co-catalyst component.

[0068] The supported catalyst prepared by the above-mentioned preparation method can be prepared as a supported catalyst in which the main catalyst component and the co-catalyst component of the catalyst solution are present in a state of being coated on the surface and pores of the support, and due to the characteristic particle size distribution of the support, most of the coated active components can be used as an effective amount, so the activity is excellent, and therefore, it is expected that the productivity of carbon nanotubes will be improved.

[0069] Method for producing carbon nanotubes

[0070] According to another aspect of the present invention, a method for producing carbon nanotubes using the above-mentioned catalyst is provided. Specifically, the present invention provides a method for producing carbon nanotubes, comprising injecting the above-mentioned supported catalyst for producing carbon nanotubes into a fluidized bed reactor, supplying a carbon source gas and a fluidizing gas to the fluidized bed reactor, and then reacting the carbon source gas and the fluidizing gas to produce the carbon nanotubes.

[0071] The supported catalyst for producing carbon nanotubes according to an embodiment of the present invention may be injected into a fluidized bed reactor, and then a carbon source gas and a fluidizing gas may be additionally supplied to the fluidized bed reactor to produce carbon nanotubes.

[0072] The carbon source gas is a carbon-containing gas that decomposes at high temperatures to form carbon nanotubes. Specific examples thereof include various carbon-containing compounds, such as aliphatic alkanes, aliphatic alkenes, aliphatic alkynes, and aromatic compounds. More specifically, compounds such as methane, ethane, ethylene, acetylene, ethanol, methanol, acetone, carbon monoxide, propane, butane, benzene, cyclohexane, propylene, butylene, isobutylene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, acetylene, formaldehyde, and acetaldehyde can be used.

[0073] The flowing gas imparts fluidity to the carbon nanotubes and catalyst particles synthesized in the fluidized bed reactor, and a gas having high thermal stability and not reacting with the carbon source gas or the carbon nanotubes can be used. For example, nitrogen or an inert gas can be used as the flowing gas.

[0074] As the fluidized bed reactor, any fluidized bed reactor known for producing carbon nanotubes can be used without particular limitation.

[0075] carbon nanotubes

[0076] The carbon nanotubes produced by the method for producing carbon nanotubes of the present invention may be bundle-type carbon nanotubes, and may have a number average particle diameter of 0 to 500 μm, preferably 40 to 300 μm, more preferably 40 to 200 μm.

[0077] The packing density of carbon nanotubes can be 10kg / m 3 Up to 80kg / m 3 , specifically 20kg / m 3Up to 80kg / m 3 , more specifically 20kg / m 3 Up to 40kg / m 3 In addition, the tap density of carbon nanotubes can be 15kg / m 3 Up to 100kg / m 3 , specifically 30kg / m 3 Up to 80kg / m 3 , more specifically 35kg / m 3 Up to 70kg / m 3 The carbon nanotubes satisfying the above range may have excellent electrical conductivity and excellent dispersibility while maintaining their original shape, and may be advantageous for preparing a highly agglomerated dispersion.

[0078] The tap density of carbon nanotubes can be measured using a typical tap density measuring device. Specifically, the tap density can be measured according to ASTM B527-06, for example, using TAS-2S manufactured by Logan Co., Ltd.

[0079] In addition, the tap density of carbon nanotubes can be measured according to a laboratory ruler, and even if the measurement is performed according to a laboratory ruler, a result substantially the same as that based on the above-mentioned standard can be obtained. Various measurement methods may be possible according to the laboratory ruler. For example, a 5mL measuring cylinder is first placed on the ruler, and then the ruler is set to zero, and then 5mL of carbon nanotubes are placed in the measuring cylinder. The volume is measured by reading the ruler at the same visual height as the height of the carbon nanotubes, and then the measuring cylinder is placed on the ruler to measure the weight of the carbon nanotubes. The measuring cylinder is tapped on the floor about 100 times, and then the volume of the carbon nanotubes is measured by reading the ruler. Then, by dividing the weight of the carbon nanotubes by the volume of the carbon nanotubes after 100 taps, the tap density (weight of carbon nanotubes (kg) / volume of carbon nanotubes after 100 taps (m 3 )).

[0080] The BET specific surface area of ​​carbon nanotubes can be 150 m 2 / g to 300m 2 / g, more specifically 160m 2 / g to 220m 2 / g. When the above range is met, dispersion can be achieved at a high concentration. Specifically, in the present invention, the specific surface area of ​​the carbon nanotubes is measured by the BET method and can be calculated from the nitrogen adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II (e.g., BEL Japan Co., Ltd.).

[0081] At the same time, the average strand diameter of the carbon nanotube units can be 30 nm or less, specifically 10 nm to 30 nm, and the average length can be 0.5 μm to 200 μm, specifically 10 μm to 60 μm. When these ranges are met, the units can have excellent electrical conductivity and strength, be stable at both room and high temperatures, and have excellent dispersibility.

[0082] The aspect ratio of the carbon nanotube unit can be 5 to 50,000, more specifically 10 to 20,000, which is defined as the ratio of the length (the length of the major axis passing through the center of the unit) to the diameter (the length of the minor axis passing through the center of the unit and perpendicular to the major axis) of the carbon nanotube unit.

[0083] In the present invention, the average strand diameter and length of the carbon nanotube units can be measured using a field emission radial scanning electron microscope.

[0084] Example

[0085] Hereinafter, the present invention will be described in more detail with reference to embodiment and experimental embodiment, but the present invention is not limited by embodiment and experimental embodiment. According to the embodiment of the present invention, it can be modified into other various forms, and the scope of the present invention should not be interpreted as being limited to the embodiment described below. The embodiments of the present invention are provided in order to more fully describe the present invention to those skilled in the art.

[0086] Examples and Comparative Examples

[0087] As an aluminum-based support precursor, aluminum hydroxide (Al(OH)3) was heat-treated at 450°C for 4 hours in an air atmosphere to prepare an aluminum-based support containing 40% by weight or more of AlO(OH). The prepared support was introduced into a classifier to obtain particles with a number average particle size of 4 μm. Separately, NH4VO3 was dissolved in water, and then 0.44 mol of citric acid was introduced thereto relative to 1 mol of NH4VO3 to prepare an NH4VO3 aqueous solution. Co(NO3)2·6H2O and the NH4VO3 aqueous solution were mixed so that the molar ratio of Co:V was 10:1, thereby preparing a catalyst solution, which was a transparent aqueous solution.

[0088] The support and the catalyst solution were mixed so that the amounts of Co and V in the catalyst solution were 16 mol and 1.6 mol, respectively, relative to 100 mol of Al in the support.

[0089] The catalyst solution was loaded onto the support in a 60°C constant temperature bath for 5 minutes and then dried in air at 120°C for 6 hours. Thereafter, it was fired in air at 720°C for 1.5 hours to prepare a supported catalyst. The content of the loaded active component at this time is shown in Table 1 below.

[0090] In addition, supported catalyst particles for preparing carbon nanotubes in the remaining examples and comparative examples were obtained in the same manner as above, except that the number average particle size of the carrier and the content of the main catalyst component in the active component were different, as shown in Table 1 below.

[0091] Experimental Example 1. Yield and Packing Density of Carbon Nanotubes

[0092] Manufacturing of carbon nanotubes

[0093] The prepared supported catalyst for producing carbon nanotubes was installed in the middle section of a cylindrical quartz fluidized bed reactor with a diameter of 55 mm. The reactor was then heated to 670°C and maintained in a nitrogen atmosphere. Nitrogen, hydrogen, and ethylene gases were then supplied at a volumetric mixing ratio of 1:1:1, totaling 300 sccm, for 60 minutes to synthesize carbon nanotubes. The yield and bulk density of carbon nanotubes synthesized using the supported catalysts of Examples and Comparative Examples were measured and are shown in Table 1 below.

[0094] Measurement method

[0095] 1) Number average particle size: The number average particle size of the prepared carrier was measured using a particle size analyzer (Microtrac, bluewave).

[0096] 2) Yield: The yield was calculated according to the following Equation 1 based on the weight of the supported catalyst used to produce carbon nanotubes and the weight increased after the reaction.

[0097] [Equation 1]

[0098] Yield (multiple) = (total weight after reaction - weight of catalyst used) / weight of catalyst used

[0099] 3) Bulk density: The powder was filled in a 5 mL container of known weight and then weighed, and the density was calculated according to Equation 2 below.

[0100] [Equation 2]

[0101] Bulk density (kg / m 3 ) = carbon nanotube weight (kg) / carbon nanotube volume (m 3 )

[0102] Measurement results

[0103] [Table 1]

[0104]

[0105] With reference to Table 1 above, in the case of Comparative Examples 1-1, 2-1, 3-1, and 4-1, in which the number average particle diameter is 1.4 μm, it is confirmed that the yield and bulk density thereof are lower than those of the Examples to which the Comparative Examples correspond, respectively. It can be seen that this is the result of a certain degree of reduction in activity due to the aggregation between the supported catalyst particles caused by the smaller number average particle diameter. In addition, when compared with Examples 1-2, 2-2, 3-2, and 4-2, in which the number average particle diameter of the carrier is 19 μm (less than 20 μm), in the case of Comparative Examples 1-2, 2-2, 3-2, and 4-2, in which the number average particle diameter of the carrier is 24 μm (greater than 20 μm), and Comparative Examples 1-3, 2-3, 3-3, and 4-3, in which the number average particle diameter of the carrier is 50 μm (greater than 20 μm), even if the size of the catalyst particles is significantly increased, the yield of carbon nanotubes remains unchanged or decreases. This means that when the number average particle size of the carrier becomes larger than the range of the present invention, the large particle size of the carrier becomes an obstacle to the loading of the active component and therefore has no favorable effect on the catalytic activity, and the loading of the active component is maximized within the number average particle size range of the carrier of the present invention, so that a supported catalyst with optimal catalytic activity while minimizing the use of catalyst raw materials can be prepared.

[0106] In addition, it has been confirmed that when the main catalyst component is loaded by increasing the content of the main catalyst component in the embodiment, as the content of the main catalyst component to be loaded increases, productivity continues to increase, and accordingly, bulk density also increases, but in the comparative example, even when the content of the main catalyst component increases, productivity does not significantly increase, on the contrary, in some cases productivity declines instead. This means that, as mentioned above, the load of active component can be maximized within the carrier number average particle size range of the present invention, however, in the case of the comparative example that does not meet the carrier number average particle size range of the present invention, active component is not evenly distributed in the carrier, and active component does not serve as effective amount.

[0107] From the above, it can be determined that according to the supported catalyst of an embodiment of the present invention, that is, in the case of a supported catalyst using a carrier having a number average particle size of 1.5 μm to 20 μm, most of the supported active components act as active components, and therefore, the catalytic activity is improved, and preventing aggregation effectively prevents the loss of activity, which helps to improve the productivity of carbon nanotubes, and it can also be confirmed that this increase in effective amount is not achieved by increasing the content of the active component, but can only be implemented by applying a carrier with an appropriate particle size distribution.

Claims

1. A supported catalyst for producing carbon nanotubes, comprising: Number average particle size (D MN ) is a carrier of 1.5 μm to 20 μm; and The active component loaded in the carrier, in, The active components include a main catalyst component and a co-catalyst component, the main catalyst component is one or more selected from nickel, cobalt and iron, and the co-catalyst component is vanadium, and Wherein, the support is an aluminum-based support containing more than 40 wt % of AlO(OH).

2. The supported catalyst according to claim 1, wherein The number average particle size of the carrier is 4.0 μm to 20 μm.

3. The supported catalyst according to claim 1, wherein The number average particle size of the carrier is 4.0 μm to 19 μm.

4. The supported catalyst according to claim 1, wherein The active component is present in an amount of 5 to 30 wt % based on the total weight of the supported catalyst for producing carbon nanotubes.

5. The supported catalyst according to claim 1, wherein The molar ratio of the main catalyst component to the co-catalyst component is 10:0.1 to 10:

10.

6. The supported catalyst according to claim 1, wherein The supported catalyst is used for preparing bundle-type carbon nanotubes.

7. A method for producing carbon nanotubes, the method comprising: injecting the supported catalyst for producing carbon nanotubes according to claim 1 into a fluidized bed reactor; and A carbon source gas and a fluidizing gas are supplied to the fluidized bed reactor, and then the carbon source gas and the fluidizing gas are reacted to produce carbon nanotubes.

8. The method of claim 7, wherein: The carbon nanotubes are bundle-type carbon nanotubes.

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