Method for producing a catalyst for producing small diameter carbon nanotubes and method for producing carbon nanotubes using the catalyst

Abstract

To provide a catalyst for preparing a carbon nanotube capable of synthesizing a low-diameter carbon nanotube, and a method for preparing the same.SOLUTION: There is provided a method for preparing a catalyst for preparing a carbon nanotube, comprising: (a) dissolving a main catalyst precursor, a support precursor, a cocatalyst precursor and a precipitation inhibitor in a solvent to prepare a precursor solution; and (b) pyrolyzing the precursor solution by spraying the precursor solution into a reactor, wherein a mole fraction of the precipitation inhibitor to the cocatalyst precursor is 0.1 to 1.5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present specification relates to a method for producing a catalyst for producing small diameter carbon nanotubes, a catalyst for producing carbon nanotubes produced thereby, a method for producing small diameter carbon nanotubes, and carbon nanotubes produced thereby. [Background technology]

[0002] As interest in and demand for environmentally friendly energy and electric vehicles increases, the demand for secondary batteries and the need for improved performance are rapidly increasing. In particular, secondary batteries for electric vehicles are required to be high-capacity secondary batteries with high energy density, long life, and low self-discharge rate, and in order to ensure such properties, it is essential to develop conductive materials with high electrical conductivity.

[0003] The conductive material acts as a path for charge transfer within the battery, and can be a carbon-based conductive material such as graphite, carbon black, graphene, carbon nanotubes, etc., with conductive carbon black being the main material used to date.

[0004] Carbon nanotubes are a material with a tube-shaped structure consisting of a hexagonal honeycomb lattice in which one carbon atom is bonded to three other carbon atoms, and are attracting attention as a next-generation conductive material for secondary batteries due to their excellent electrical conductivity. When carbon nanotubes are used as a conductive material, the energy density and life characteristics of secondary batteries can be improved and the size of the battery can be reduced.

[0005] Meanwhile, since carbon nanotubes have better electrical conductivity as their diameters become smaller, when small-diameter carbon nanotubes are used as conductive materials for secondary batteries, the capacity and life characteristics of the secondary batteries can be further improved. Therefore, there is a need to develop a catalyst for synthesizing carbon nanotubes having a smaller diameter than conventional ones and a carbon nanotube manufacturing technology using the catalyst. Summary of the Invention [Problem to be solved by the invention]

[0006] The present specification is intended to solve the problems of the prior art described above, and one object of the present specification is to provide a catalyst for producing carbon nanotubes that can synthesize small diameter carbon nanotubes and a method for producing the same.

[0007] Another object of the present invention is to provide small diameter carbon nanotubes having excellent electrical conductivity and a method for producing the same. [Means for solving the problem]

[0008] According to one aspect, there is provided a method for producing a catalyst for producing carbon nanotubes, comprising: (a) dissolving a main catalyst precursor, a support precursor, a co-catalyst precursor, and a precipitation inhibitor in a solvent to prepare a precursor solution; and (b) spraying the precursor solution into a reactor and pyrolyzing it, wherein a molar fraction of the precipitation inhibitor relative to the co-catalyst precursor is 0.1 to 1.5.

[0009] In one embodiment, the main catalyst precursor may be one or more metal precursors selected from Co, Fe and Ni.

[0010] In one embodiment, the support precursor may be one or more metal precursors selected from Al, Ca, and Mg.

[0011] In one embodiment, the promoter precursor may be one or more metal precursors selected from V, Mn and Mo.

[0012] In one embodiment, the precipitation inhibitor may be one selected from the group consisting of citric acid, tricarballylic acid, mercaptosuccinic acid, succinic acid, and combinations thereof.

[0013] In another aspect, there is provided a catalyst for producing carbon nanotubes, which is produced by the method for producing a catalyst for producing carbon nanotubes.

[0014] In an embodiment, the catalyst for synthesizing carbon nanotubes may have an apparent density of 0.02 to 0.2 g / ml.

[0015] In an embodiment, the catalyst for synthesizing carbon nanotubes may have a spherical particle shape.

[0016] According to another aspect, there is provided a method for producing carbon nanotubes, comprising: (1) introducing the catalyst for producing carbon nanotubes into a chemical vapor deposition reactor; and (2) injecting a carbon source gas to synthesize carbon nanotubes.

[0017] In one embodiment, the carbon source gas may include one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, and a mixture of two or more thereof.

[0018] According to yet another aspect, there is provided a carbon nanotube produced by the method for producing a carbon nanotube.

[0019] In one embodiment, the carbon nanotubes may have a diameter of 7 to 12 nm.

[0020] In one embodiment, the purity of the carbon nanotubes may be greater than 90%.

[0021] In one embodiment, the carbon nanotube bundle may have a length of 50 to 200 μm.

[0022] In one embodiment, the BET specific surface area of ​​the carbon nanotubes is 250 to 400 m 2 / g.

[0023] In one embodiment, the apparent density of the carbon nanotubes may be 0.005 to 0.5 g / ml. Effect of the Invention

[0024] One of the various advantages of the present invention is that it provides a catalyst for producing carbon nanotubes that can be used to synthesize small diameter carbon nanotubes having a reduced diameter compared to conventional catalysts.

[0025] Another advantage of the present invention is that the catalyst for producing carbon nanotubes can be produced with a high yield since the precipitation of catalyst components during the preparation of the catalyst precursor solution can be prevented.

[0026] Yet another of the many advantages of the present invention is that small diameter carbon nanotubes can be synthesized with high purity.

[0027] Another advantage of the present invention is that it is possible to provide carbon nanotubes that have excellent electrical conductivity due to their small diameter, and thus can improve the capacity and life characteristics of secondary batteries when used as a conductive material for secondary batteries.

[0028] The effects of this specification are not limited to the effects described above, but should be understood to include all effects that can be inferred from the configurations described in the detailed description of this specification or the claims. [Brief description of the drawings]

[0029] [Figure 1] 1 is a SEM image of a catalyst prepared according to Example 1 of the present specification. [Diagram 2] 1 is a SEM image of a catalyst prepared according to Example 2 of the present specification. [Diagram 3] 1 is a SEM image of a catalyst prepared according to Example 3 herein. [Figure 4] 1 is a SEM image of a catalyst prepared according to Comparative Example 3 herein. [Diagram 5] 1 is a SEM image of a catalyst prepared according to Comparative Example 4 herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an aspect of the present specification will be described with reference to the accompanying drawings. However, the description of the present specification may be embodied in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe an aspect of the present specification in the drawings, parts that are not related to the description are omitted, and similar parts are designated by similar reference numerals throughout the specification.

[0031] Throughout the specification, when a part is described as being "connected" to another part, this includes not only the case where the part is "directly connected" to another part, but also the case where the part is "indirectly connected" to another part through another member in between. Furthermore, when a part is described as "comprising" some component, this does not mean that the part excludes other components, but that the part may further comprise other components, unless otherwise specified.

[0032] When a range of numerical values ​​is given herein, unless a specific range is stated otherwise, the values ​​have the precision of the significant figures provided by standard rules in chemistry for significant figures, for example, the number 10 includes a range of 5.0 to 14.9, and the number 10.0 includes a range of 9.50 to 10.49.

[0033] Hereinafter, an embodiment of the present specification will be described in detail with reference to the accompanying drawings.

[0034] Method for producing catalyst for producing carbon nanotubes A method for producing a catalyst for producing carbon nanotubes according to one aspect of the present specification includes: (a) dissolving a main catalyst precursor, a support precursor, a co-catalyst precursor, and a precipitation inhibitor in a solvent to prepare a precursor solution; and (b) spraying the precursor solution into a reactor and pyrolyzing it; wherein the molar fraction of the precipitation inhibitor relative to the co-catalyst precursor is 0.1 to 1.5.

[0035] The crystal structure of the catalyst for synthesizing carbon nanotubes may vary depending on the method for producing the catalyst or the ratio of components constituting the catalyst. The growth morphology and characteristics of carbon nanotubes synthesized using the catalyst may vary depending on the crystal structure of the catalyst.

[0036] The method for producing the catalyst for producing carbon nanotubes uses a spray pyrolysis method to produce a catalyst having a spherical particle shape, and a catalyst having a lower apparent density than a catalyst produced by a support method.

[0037] In addition, the catalyst prepared using the spray pyrolysis method may have a hollow structure, in which the thickness of the hollow may be 0.5 to 10 μm, preferably 1 to 8 μm, and the hollow ratio may be 50% by volume or more. Here, the hollow structure means a structure with an open space inside, for example, a spherical or polyhedral structure with an open space inside, and includes a closed structure in which the hollow space is completely sealed, an open structure in which a part of the hollow space is open, or a combination thereof. When the catalyst has a hollow structure as described above, it may be advantageous for the synthesis of small diameter carbon nanotubes.

[0038] By using the catalyst prepared by the above method, small diameter carbon nanotubes having a smaller diameter than conventional ones can be synthesized, and the diameter of the small diameter carbon nanotubes can be 7 to 12 nm. Carbon nanotubes synthesized by using the catalyst prepared by the above method have low apparent density and excellent electrical conductivity, so that when used as a conductive material for secondary batteries, the capacity and life characteristics of the secondary batteries can be improved.

[0039] The method for producing a catalyst for producing carbon nanotubes can produce a catalyst for producing carbon nanotubes with a high yield by suppressing precipitation of catalyst components during preparation of a precursor solution.

[0040] The catalyst production yield using the method for producing a catalyst for producing carbon nanotubes may be 90% or more, for example, 90%, 91%, 92%, 93%, 94%, 95% or more, but is not limited thereto. If the catalyst production yield is below the above range, the economic efficiency of the catalyst production process may decrease.

[0041] The method for preparing a catalyst for preparing carbon nanotubes can be used to synthesize small diameter carbon nanotubes having a smaller diameter than conventional ones by controlling the molar fraction of the precipitation inhibitor relative to the cocatalyst precursor. The diameter of the carbon nanotubes synthesized using the catalyst prepared by the method can be 7 to 12 nm, and since it exhibits low apparent density and excellent electrical conductivity, when used as a conductive material for secondary batteries, it can improve the capacity and life characteristics of the secondary batteries.

[0042] The molar fraction of the precipitation inhibitor relative to the cocatalyst precursor may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range between these values. If the molar fraction of the precipitation inhibitor relative to the cocatalyst precursor is less than the above range, the catalyst components may be precipitated during the preparation of the precursor solution, and the catalyst for preparing carbon nanotubes may not be prepared. If the molar fraction of the precipitation inhibitor relative to the cocatalyst precursor exceeds the above range, the catalyst preparation yield may decrease, and the diameter of the carbon nanotubes synthesized using the prepared catalyst may increase, and the electrical conductivity may decrease, making the catalyst unsuitable as a conductive material for secondary batteries.

[0043] Step (a) is a step of preparing a precursor solution containing precursors of metal components contained in a catalyst for producing carbon nanotubes, and may include a step of adding a main catalyst precursor, a support precursor, a co-catalyst precursor and a precipitation inhibitor to a solvent and then stirring under a nitrogen atmosphere.

[0044] The main catalyst precursor may be, but is not limited to, one or more metal precursors selected from Co, Fe, and Ni.

[0045] The support precursor may be one or more metal precursors selected from Al, Ca and Mg, but is not limited thereto.

[0046] The promoter precursor may be one or more metal precursors selected from V, Mn and Mo, but is not limited thereto.

[0047] The metal precursor may be one selected from the group consisting of nitrates, sulfates, alkoxides, chlorides, acetates, carbonates, and mixtures of two or more of the above metals, but is not limited thereto.

[0048] The precipitation inhibitor serves to smoothly dissolve the main catalyst precursor, the support precursor and the co-catalyst precursor in the solvent.

[0049] The precipitation inhibitor may be an organic acid, for example, but is not limited to, a carboxylic acid.

[0050] The precipitation inhibitor may be one selected from the group consisting of citric acid, tricarballylic acid, mercaptosuccinic acid, succinic acid, and combinations thereof, but is not limited thereto.

[0051] In step (a), the solvent may be a polar solvent, and the polar solvent may be water, methanol, ethanol, propanol, isopropanol, butanol, or a mixture of two or more of these, for example, deionized water, but is not limited thereto. When deionized water is used as the solvent, impurities in the precursor solution can be minimized, and thus the purity of the finally produced catalyst can be improved. The improvement in the purity of the catalyst can result in the improvement in the purity of the carbon nanotubes.

[0052] The step (b) may include: (b1) spraying the precursor solution into a reactor together with a carrier gas; and (b2) pyrolyzing the sprayed precursor solution at 600 to 1,200°C.

[0053] In step (b1), the precursor solution may be converted into finer droplets by spraying it into the reactor in order to control the particle shape, apparent density, etc. of the catalyst.

[0054] In the step (b1), the carrier gas may be air, but is not limited thereto.

[0055] In the step (b2), the droplets are heated to evaporate the solvent and decompose the precursor to produce a catalyst.

[0056] In the step (b2), the temperature of the reactor may be 600 to 1,200°C. For example, it may be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1,000°C, 1,050°C, 1,100°C, 1,150°C, 1,200°C, or a range between these values. If the temperature of the reactor is lower than the above range, the drying state of the catalyst is poor and an additional process is required, which is economically disadvantageous, and the purity and physical properties of the carbon nanotubes synthesized using the same may be reduced. If the temperature of the reactor is higher than the above range, not only will excessive costs be required for the construction of equipment or facilities, resulting in economic losses, but the performance of the catalyst may be reduced due to the formation of a solid solution or deformation of the crystal structure.

[0057] Catalyst for producing carbon nanotubes A catalyst for producing carbon nanotubes according to another aspect of the present specification is produced by the above-mentioned method for producing a catalyst for producing carbon nanotubes.

[0058] The bulk density of the catalyst for producing carbon nanotubes may be 0.02 to 0.2 g / ml. For example, it may be 0.02 g / ml, 0.03 g / ml, 0.04 g / ml, 0.05 g / ml, 0.06 g / ml, 0.07 g / ml, 0.08 g / ml, 0.09 g / ml, 0.10 g / ml, 0.11 g / ml, 0.12 g / ml, 0.13 g / ml, 0.14 g / ml, 0.15 g / ml, 0.16 g / ml, 0.17 g / ml, 0.18 g / ml, 0.19 g / ml, 0.20 g / ml, or a range between both values ​​thereof. The bulk density may be measured using a powdered catalyst. If the apparent density is outside the above range, the synthesis yield and purity of the carbon nanotubes synthesized using the catalyst may decrease, or the diameter may increase, making the carbon nanotubes unsuitable as a conductive material for secondary batteries.

[0059] The catalyst for producing carbon nanotubes may have a spherical particle shape. The spherical catalyst particles may have an average aspect ratio of 1.2 or less. The aspect ratio refers to the value obtained by dividing the length of the longest part of the catalyst particle (long axis length) by the length of the smallest part (short axis length).

[0060] The catalyst for synthesizing carbon nanotubes may have a porous structure including pores, and the pores may have a size of 1 to 10 nm.

[0061] Method for producing carbon nanotubes A method for producing carbon nanotubes according to another aspect of the present specification includes: (1) introducing the above-mentioned catalyst for producing carbon nanotubes into a chemical vapor deposition reactor; and (2) injecting a carbon source gas to synthesize carbon nanotubes.

[0062] The chemical vapor deposition reactor may be, but is not limited to, a fixed-bed chemical vapor deposition reactor or a fluidized-bed chemical vapor deposition reactor.

[0063] The carbon source gas may include one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, and a mixture of two or more of these. For example, methane (CH 4 ), ethane (C 2 H 6 ), ethylene (C 2 H 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ), acetylene (C 2 H 2 ), carbon monoxide (CO), or a mixture of two or more thereof.

[0064] In step (2), the internal temperature of the chemical vapor deposition reactor may be 600 to 1,000° C. For example, it may be 600° C., 650° C., 700° C., 750° C., 800° C., 850° C., 900° C., 950° C., 1,000° C., or a range between any two of these values. If the internal temperature of the reactor is below this range, the growth of carbon nanotubes may be impossible or delayed, and if it exceeds this range, the synthesized carbon nanotubes may be thermally decomposed or may bond to each other and not maintain their shape.

[0065] The ratio of the flow rate (L / min) of the carbon source gas to the input amount (g) of the catalyst for synthesizing carbon nanotubes may be 0.1 to 1.1 L / g·min. For example, it may be 0.1 L / g·min, 0.2 L / g·min, 0.3 L / g·min, 0.4 L / g·min, 0.5 L / g·min, 0.6 L / g·min, 0.7 L / g·min, 0.8 L / g·min, 0.9 L / g·min, 1.0 L / g·min, 1.1 L / g·min, or a range between these values. If the ratio of the flow rate of the carbon source gas to the input amount of the catalyst is less than the above range, the catalytic activity may be excessively reduced, and carbon nanotubes may not be synthesized. If it exceeds the above range, the diameter of the synthesized carbon nanotubes may increase and the electrical conductivity may be reduced, making them unsuitable as a conductive material for secondary batteries.

[0066] In step (2), the carbon source gas may be injected together with a carrier gas, which may be, but is not limited to, one selected from the group consisting of helium, nitrogen, argon, and a mixture of two or more thereof.

[0067] In the step (2), the synthesis of carbon nanotubes may be performed by permeating and saturating a carbon source gas decomposed by high temperature heat into the catalyst, followed by deposition of carbon.

[0068] Carbon Nanotubes Carbon nanotubes according to yet another aspect of the present specification are produced by the above-mentioned method for producing carbon nanotubes.

[0069] The diameter of the carbon nanotube may be 7 to 12 nm, for example, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, or a range between these values. If the diameter is less than the above range, the carbon nanotube may have structural defects or poor dispersibility, and if the diameter exceeds the above range, the electrical conductivity may be reduced, and when used as a conductive material for a secondary battery, the energy density, life characteristics, and self-discharge rate of the secondary battery may be reduced.

[0070] The carbon nanotubes may have a purity of 90% or more. If the purity is less than this range, the electrical conductivity may be reduced, and when used as a conductive material for a secondary battery, impurities may react inside the battery, causing a safety accident.

[0071] The carbon nanotube may be, but is not limited to, a bundle-type carbon nanotube in which a plurality of carbon nanotubes are aggregated together.

[0072] The length of the carbon nanotube bundle may be 50 to 200 μm. For example, it may be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, or a range between these values. If the bundle length is less than the above range, the electrical conductivity may decrease, making it unsuitable as a conductive material for secondary batteries, and if it exceeds the above range, the dispersibility may decrease.

[0073] The BET specific surface area of ​​the carbon nanotubes is 250-400m 2 For example, 250 m 2 / g, 260m 2 / g, 270m 2 / g, 280m 2 / g, 290m 2 / g, 300m 2 / g, 310m 2 / g, 320m 2 / g, 330m 2 / g, 340m 2 / g, 350m 2 / g, 360m 2 / g, 370m 2 / g, 380m 2 / g, 390m 2 / g, 400m 2 If the BET specific surface area is less than the above range, the electrical conductivity may be reduced, making the conductive material unsuitable for use in secondary batteries, whereas if the BET specific surface area is more than the above range, the dispersibility may be reduced.

[0074] The bulk density of the carbon nanotubes may be 0.005 to 0.5 g / ml. For example, it may be 0.005 g / ml, 0.01 g / ml, 0.02 g / ml, 0.03 g / ml, 0.04 g / ml, 0.05 g / ml, 0.06 g / ml, 0.07 g / ml, 0.08 g / ml, 0.09 g / ml, 0.1 g / ml, 0.2 g / ml, 0.3 g / ml, 0.4 g / ml, 0.5 g / ml, or a range between these values. The bulk density may be measured using powdered carbon nanotubes. If the bulk density is less than the range, dispersibility may decrease, and if it exceeds the range, backside electrical conductivity may decrease, making it unsuitable as a conductive material for secondary batteries.

[0075] The carbon nanotubes exhibit excellent electrical conductivity, and therefore, when used as a conductive material for secondary batteries, even a small amount can exhibit the same or improved performance compared to existing materials. As a result, the carbon nanotubes can be applied to the production of high-capacity secondary batteries with high energy density, long life, and low self-discharge rate.

[0076] The examples of the present specification will be described in more detail below. However, the following experimental results are only representative experimental results among the above examples, and the scope and content of the present specification should not be construed as being narrowed or limited by the examples. The respective effects of various embodiments of the present specification that are not explicitly presented below will be specifically described in the relevant parts.

[0077] Example 1 Co(NO 3 ) 3 6H 2 O 0.78 mol, Al(NO 3 ) 3 9H 2 2.28 mol O, NH 4 VO 3 A precursor mixture solution was prepared by dissolving 0.09 mol of cadmium hydroxide and 0.135 mol of citric acid in deionized water, and then spraying the precursor mixture solution into a reactor at 750° C. and pyrolyzing it to prepare a catalyst.

[0078] Example 2 The catalyst was prepared in the same manner as in Example 1, except that 0.09 mol of citric acid was used.

[0079] Example 3 The catalyst was prepared in the same manner as in Example 1, except that 0.009 mol of citric acid was used.

[0080] Comparative Example 1 The catalyst was prepared in the same manner as in Example 1, except that 0.2 mol of citric acid was used.

[0081] Comparative Example 2 The catalyst was prepared in the same manner as in Example 1, except that 0.0072 mol of citric acid was used.

[0082] Comparative Example 3 Co(NO 3 ) 3 6H 2 0.78 mol O, NH 4 VO 3 The precursor mixture solution was prepared by dissolving 0.09 mol of ZnO and 0.09 mol of citric acid in deionized water. The precursor mixture solution was then placed on a solid support, alumina (Al 2 O 3 ) and then calcined at 700° C. for 3 hours to prepare a supported catalyst.

[0083] Comparative Example 4 A supported catalyst was prepared in the same manner as in Comparative Example 3, except that 0.009 mol of citric acid was used.

[0084] Table 1 below shows the citric acid content, the molar fraction of citric acid relative to the cocatalyst, and the catalyst preparation method used in Examples 1 to 3 and Comparative Examples 1 to 4.

[0085] [Table 1]

[0086] Manufacturing Example Each of the catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was loaded into a 350 mm fluidized bed chemical vapor deposition reactor, and the internal temperature of the reactor was raised to 650 to 800° C. under a nitrogen atmosphere, and then a carbon source gas was injected to synthesize carbon nanotubes. At this time, the flow rate of the carbon source gas was kept constant at 0.3 L / min per 1 g of catalyst.

[0087] Experimental Example 1 The particle morphology, production yield rate and apparent density of the catalysts produced in the above examples and comparative examples were measured, and the results are shown in the following Tables 2 and 3 and FIGS.

[0088] 1) Particle morphology: Measured at 300x magnification using FE-SEM (JEOL, JSM-7500F).

[0089] 1 to 5 show SEM images of the catalysts produced in Examples 1 to 3 and Comparative Examples 3 and 4, respectively.

[0090] 2) Production yield rate: The amount of catalyst produced compared to the total amount of metal components among the input raw materials, calculated according to the following formula.

[0091] Production yield rate (%) = amount of catalyst produced (g) / total amount of metal components among raw materials input (g) × 100.

[0092] 3) Apparent density: A 100 ml container of known weight was filled with catalyst powder, the weight was measured, and the apparent density was calculated using the following formula.

[0093] Apparent density = total amount of catalyst produced (g) / volume of catalyst produced (ml).

[0094] Experimental Example 2 The catalyst yield, average diameter and apparent density of the carbon nanotubes synthesized in the above Preparation Examples were measured, and the results are shown in Tables 2 and 3 below.

[0095] 1) Catalyst yield rate: the total amount of synthesized carbon nanotubes relative to the amount of catalyst input, calculated according to the following formula:

[0096] Catalyst yield rate (%) = total amount of carbon nanotubes synthesized (g) / catalyst input (g) × 100.

[0097] 2) Average diameter: Measured at a magnification of 200,000 times using a TEM (JEOL, JEM-2100F).

[0098] 3) Apparent density: A 100 ml container with a known weight was filled with carbon nanotube powder, the weight was measured, and the apparent density was calculated using the following formula.

[0099] Apparent density = total amount of synthesized carbon nanotubes (g) / volume of synthesized carbon nanotubes (ml)

[0100] [Table 2]

[0101] Referring to Table 2, the catalysts prepared according to Examples 1 to 3 showed a high catalyst production yield of 95%, and the carbon nanotubes synthesized using each catalyst had a reduced diameter of 7 to 12 nm and showed a high catalyst yield.

[0102] The catalyst prepared according to Comparative Example 1, in which an excessive amount of citric acid, a precipitation inhibitor, was added, had a low catalyst production yield rate, and the diameter of carbon nanotubes synthesized using the catalyst exceeded 12 nm.

[0103] In the case of Comparative Example 2, in which a small amount of citric acid, a precipitation inhibitor, was added, catalyst components were precipitated during the preparation of the precursor solution, and catalyst particles were not synthesized.

[0104] [Table 3]

[0105] 1-3, all of the catalysts prepared according to Examples 1-3 had spherical particle morphology and showed lower apparent density compared to the Comparative Example. It was confirmed that the carbon nanotubes synthesized using each catalyst had a reduced diameter of 7-12 nm and a lower apparent density.

[0106] 4 and 5, the supported catalysts prepared according to Comparative Examples 3 and 4 exhibited granular particle morphology and high apparent density. It was confirmed that the carbon nanotubes synthesized using each catalyst had a diameter of more than 12 nm and high apparent density.

[0107] Although the main catalyst and co-catalyst components and the molar fraction of the precipitation inhibitor relative to the co-catalyst precursor were the same as those of Comparative Examples 3 and 4, Examples 2 and 3 exhibited different catalyst particle morphology and apparent density due to the difference in the catalyst preparation method. In addition, it was confirmed that when carbon nanotubes were synthesized using the corresponding catalysts, the diameters and apparent densities of the synthesized carbon nanotubes were different.

[0108] The above description of the present specification is for illustrative purposes only, and a person having ordinary skill in the art to which one aspect of the present specification belongs can easily understand that the present specification can be easily modified into other specific forms without changing the technical ideas and essential features described in the present specification. Therefore, the above-described embodiments should be understood to be illustrative and not limiting in all respects. For example, each component described as a single type may be implemented in a distributed form, and similarly, each component described as a distributed type may be implemented in a combined form.

[0109] The scope of this specification is defined by the claims set forth below, and all modifications and variations that fall within the meaning and scope of the claims and their equivalent concepts should be construed as being included within the scope of this specification.

Claims

1. (a) dissolving a main catalyst precursor, a support precursor, a cocatalyst precursor, and a precipitation inhibitor in a solvent to prepare a precursor solution; and (b) spraying the precursor solution into a reactor and pyrolyzing it; A method for producing a catalyst for producing carbon nanotubes, wherein a molar fraction of the precipitation inhibitor relative to the co-catalyst precursor is 0.1 to 1.5, The main catalyst precursor is a metal precursor of Co, the support precursor is a metal precursor of Al, the co-catalyst precursor is a metal precursor of V, and the precipitation inhibitor is citric acid.

2. 2. The method for producing a catalyst for producing carbon nanotubes according to claim 1, wherein the catalyst for producing carbon nanotubes has an apparent density of 0.02 to 0.2 g / ml.

3. The method for producing a catalyst for producing carbon nanotubes according to claim 1 , wherein the catalyst particles have a spherical shape.

4. (1) preparing a catalyst for producing carbon nanotubes by the method for preparing a catalyst for producing carbon nanotubes according to any one of claims 1 to 3, and introducing the obtained catalyst for producing carbon nanotubes into a chemical vapor deposition reactor; and (2) injecting a carbon source gas to synthesize carbon nanotubes.

5. 5. The method for producing carbon nanotubes according to claim 4, wherein the carbon source gas comprises one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, and a mixture of two or more thereof.

6. The method for producing carbon nanotubes according to claim 4, wherein the diameter of the carbon nanotubes is 7 to 12 nm.

7. 5. The method for producing carbon nanotubes according to claim 4, wherein the length of the bundle of carbon nanotubes is 50 to 200 μm.

8. The BET specific surface area of ​​the carbon nanotubes is 250 to 400 m ２ The method for producing carbon nanotubes according to claim 4, wherein the molecular weight of the carbon nanotube is 1 / g.

9. The method for producing carbon nanotubes according to claim 4, wherein the apparent density of the carbon nanotubes is 0.005 to 0.5 g / ml.

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