Method for producing catalyst for producing carbon nanotubes

Abstract

The present invention relates to a method for producing a catalyst capable of producing carbon nanotubes having a higher bulk density by supporting a catalyst component under pressurized conditions, and a method for producing carbon nanotubes using the catalyst.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a catalyst for producing carbon nanotubes, which enables high-density carbon nanotubes to be produced. [Background technology]

[0002] Carbon nanomaterials include fullerenes, carbon nanotubes (CNTs), graphene, and graphite nanoplates, depending on the shape of the material. Of these, carbon nanotubes are giant molecules in which a hexagonal honeycomb-shaped graphite surface, in which one carbon atom is bonded to three different carbon atoms, is rolled up with a nano-sized diameter.

[0003] Carbon nanotubes are hollow and lightweight, with electrical conductivity as good as copper, thermal conductivity as good as diamond, and tensile strength comparable to that of steel. Depending on the coiled form, they can be divided into single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and rope carbon nanotubes.

[0004] Recently, research into carbon nanotube synthesis technology that can simultaneously synthesize large quantities of carbon nanotubes has been actively conducted, and among the various methods, chemical vapor deposition (CVD) using a fluidized bed reactor is the most popular in the industrial field because it allows for the easy synthesis of large quantities of carbon nanotubes.

[0005] Specifically, in the chemical vapor deposition method, a particulate catalyst for producing carbon nanotubes is packed into a fluidized bed reactor, and then a carbon source gas and a fluidizing gas are injected into the fluidized bed reactor to suspend the catalyst.The reactor is then heated, and the carbon source gas is decomposed on the surface of the suspended catalyst, thereby synthesizing carbon nanotubes.

[0006] In the process of producing carbon nanotubes using chemical vapor deposition, catalyst activity is a major factor that determines the productivity of the overall production process, and therefore, active research is being conducted on catalysts with higher activity and methods for producing such catalysts. For example, it is known that catalyst activity can be further improved by increasing the loading amount of the main catalyst component on the support or by supporting a promoter component. However, if an excessive amount of the main catalyst component is loaded together with the promoter, the promoter may hinder the dispersion of the main catalyst component, and there is a limit to how much the main catalyst loading can be used to increase catalytic activity.

[0007] Therefore, further research is needed to find a method for optimizing the manufacturing process of a catalyst for producing carbon nanotubes and further improving the activity of the final catalyst. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] KR10-2015-0007266A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is intended to solve the above problems and to provide a novel method for producing a catalyst for producing carbon nanotubes, which enables the production of high bulk density carbon nanotubes by applying pressure in the mixing step during the catalyst production process. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a method for producing a catalyst for producing carbon nanotubes and a method for producing carbon nanotubes.

[0011] Specifically, (1) the present invention provides a method for producing a catalyst for producing carbon nanotubes, comprising the steps of: (S1) mixing a catalyst-supported liquid with a support to obtain a mixture; (S2) drying the mixture; and (S3) calcining the dried mixture to obtain a supported catalyst, wherein the step S1 is carried out at 1.5 to 4.5 bar.

[0012] (2) The present invention provides the method for producing a catalyst for producing carbon nanotubes according to (1), wherein the step S1 is carried out at 2 to 4 bar.

[0013] (3) The present invention provides a method for producing a catalyst for producing carbon nanotubes according to (1) or (2), wherein the catalyst-supporting liquid contains a precursor of a main catalytic metal selected from the group consisting of Co, Ni, and Fe.

[0014] (4) The present invention provides a method for producing a catalyst for producing carbon nanotubes, in any one of (1) to (3), wherein the catalyst-supporting liquid contains a precursor of a promoter metal selected from the group consisting of Mo and V.

[0015] (5) The present invention provides a method for producing a catalyst for producing carbon nanotubes according to any one of (1) to (4), wherein the molar ratio of the main catalyst metal precursor to the promoter catalyst metal precursor in the catalyst support liquid is 5:1 to 20:1.

[0016] (6) The present invention provides a method for producing a catalyst for producing carbon nanotubes according to any one of (1) to (5) above, wherein the support is one or more metal oxides or hydroxides selected from the group consisting of aluminum, magnesium, calcium, and silicon.

[0017] (7) In any one of the above (1) to (6), the present invention is characterized in that the specific surface area of ​​the support is 100 to 1000 m 2 / g of a catalyst for producing carbon nanotubes.

[0018] (8) The present invention provides a method for producing a catalyst for producing carbon nanotubes according to any one of the above (1) to (7), wherein the step S2 is carried out under normal pressure or reduced pressure conditions.

[0019] (9) The present invention provides the method for producing a catalyst for producing carbon nanotubes according to any one of the above (1) to (8), wherein the step S2 is carried out at 10 to 100 mbar.

[0020] (10) The present invention provides the method for producing a catalyst for producing carbon nanotubes according to any one of the above (1) to (9), wherein the step S2 is carried out at a temperature of 50 to 200°C.

[0021] (11) The present invention provides the method for producing a catalyst for producing carbon nanotubes according to any one of (1) to (10), wherein the step S3 is carried out at a temperature of 600 to 800° C. for 0.5 to 3 hours.

[0022] (12) The present invention provides a method for producing carbon nanotubes, comprising the steps of: (S1) mixing a catalyst support liquid with a support to obtain a mixture; (S2) drying the mixture; (S3) calcining the dried mixture to obtain a supported catalyst; (S4) introducing the obtained catalyst into a chemical vapor deposition reactor; and (S5) injecting a carbon source gas into the reactor, heating it, and synthesizing carbon nanotubes, wherein the step S1 is carried out at 1.5 to 4.5 bar. [Effects of the Invention]

[0023] When carbon nanotubes are produced using the catalyst produced by the production method of the present invention, the final carbon nanotubes have a high bulk density, and therefore more carbon nanotubes can be produced based on the same reaction volume. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in more detail.

[0025] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0026] The term "carbon nanotube" used in the present invention refers to a secondary structure formed by the complete or partial assembly of carbon nanotube units. The carbon nanotube units are graphite sheets with a cylindrical shape of nanometer-sized diameter and an sp2 bond structure. Depending on the angle and structure of the graphite sheet, the carbon nanotube units can exhibit conductive or semiconductive properties. Depending on the number of bonds forming the wall, carbon nanotube units are classified as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs). The thinner the wall, the lower the resistance.

[0027] The carbon nanotube of the present invention may include one or more of single-wall, double-wall, and multi-wall carbon nanotube units.

[0028] Method for producing catalyst for producing carbon nanotubes Catalysts used in the synthesis of carbon nanotubes using chemical vapor deposition (CVD) can be prepared in the form of solid particles by various methods, but are generally prepared using a support method, in which a metal component is supported on a support. In particular, catalyst preparation methods using a support method are most widely used in the industrial field because they allow for the production of large quantities of catalyst in a shorter time than catalyst preparation methods using physical or chemical vapor deposition, have lower production costs, and exhibit good catalyst activity. Furthermore, recently, a method of preparing a catalyst using a support method and supporting a promoter component together with the main catalyst component to improve the activity of the catalyst component has become popular.

[0029] However, in the case of catalysts prepared using the support method, the amount of catalyst that can be supported is limited by the physical characteristics of the support itself, making it difficult to increase catalytic activity beyond a certain level. In particular, even when both a co-catalyst and a main catalyst are supported, an excessive amount of the co-catalyst can actually reduce the activity of the main catalyst. Therefore, it is necessary to maintain an appropriate ratio of the main catalyst to the co-catalyst and to prepare the catalyst within a range of main catalyst and co-catalyst contents that maximizes catalytic activity. In this regard, active research is being conducted on the optimal range of main catalyst and co-catalyst contents and the structural characteristics of the support that can further increase the support amount.

[0030] Meanwhile, as a result of research starting from this problem, the inventors of the present invention found that when pressure is applied during the loading process, the catalyst components move more to the inner region of the support, thereby improving the activity of the final catalyst and increasing the bulk density of the carbon nanotubes produced from the catalyst, which led to the completion of the present invention.

[0031] Therefore, the present invention provides a method for producing a catalyst for producing carbon nanotubes, comprising the steps of: (S1) mixing a catalyst-supported liquid with a support to obtain a mixture; (S2) drying the mixture; and (S3) calcining the dried mixture to obtain a supported catalyst, wherein the step S1 is carried out at 1.5 to 4.5 bar.

[0032] The support used in the method for producing a catalyst for carbon nanotubes of the present invention, the catalyst-supporting liquid, and each step of the production method will be described in detail below.

[0033] support body The support used in the catalyst production method of the present invention can be one or more metal oxides or hydroxides selected from the group consisting of aluminum, magnesium, calcium, and silicon, and is particularly preferably aluminum oxide or aluminum hydroxide. Such metal oxides are porous and have a large specific surface area, which allows them to exhibit high catalytic activity when supporting catalyst components. Their excellent mechanical strength also prevents phenomena such as the collapse of catalyst particles during the carbon nanotube production process. Aluminum oxide is particularly preferred because it allows for easy support of catalyst components and has excellent durability.

[0034] The support has a specific surface area of ​​100 to 1000 m 2 / g, preferably 150 to 600m 2 / g. When the specific surface area of ​​the support is within the above range, there is an advantage that the activity of the catalyst can be increased and durability can be maintained at a good level. Meanwhile, the specific surface area can be measured by the BET method, and more specifically, it can be calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77K) using a BELSORP-mini II manufactured by BEL Japan.

[0035] The support may have a D50 of 10 to 70 μm and a D90 of 20 to 90 μm, preferably a D50 of 20 to 60 μm and a D90 of 30 to 80 μm. The support may also have a bulk density of 300 to 1200 kg / m 3 Preferably, the bulk density is 500 to 1000 kg / m 3 When the physical properties of the support satisfy the above ranges, the durability of the catalyst including the support can be excellent, and the size and physical properties of the carbon nanotubes produced from the catalyst can be excellent. Meanwhile, the D50 and D90 can be measured using a laser diffraction particle size analyzer (Microtrac, S3500), and the bulk density can be calculated by filling a 5 ml cylinder with the support to be measured, measuring the volume by reading the scale, and then placing it on the scale and dividing the weight by the previously measured volume.

[0036] The shape of the support is not particularly limited, but may be spherical or potato-shaped. The support may have a porous structure, a molecular structure, a honeycomb structure, or the like so as to have a relatively high surface area per unit mass or unit volume.

[0037] Catalyst support liquid In the catalyst manufacturing method of the present invention, a catalyst supporting solution is used to support an active component that essentially functions as a catalyst on a support. The catalyst supporting solution may include a main catalyst component that can exhibit catalytic activity and a promoter component that can enhance the catalytic activity of the main catalyst component.

[0038] The main catalyst component may be one or more selected from the group consisting of Co, Ni, and Fe, and is preferably Co. The main catalyst component plays a role in lowering the activation energy of the reaction in which the carbon source gas is decomposed to form carbon nanotubes, thereby facilitating the reaction, and the above-mentioned main catalyst component has the advantages of high catalytic activity and good durability.

[0039] The main catalyst component may be contained in the form of a precursor in the catalyst support solution. Specifically, the main catalyst precursor may include a halide, nitride, oxide, nitrate, sulfate, sulfide, hydroxide, or metal salt of the main catalyst component. More specifically, for Co, Co(NO3)2·6H2O, Co2(CO)8, [Co2(CO)6(t-BuC=CH)], Co(OAc)2, or CoCl2·6H2O may be used. For Fe, Fe(NO3)2·6H2O, Fe(NO3)2·9H2O, Fe(NO3)3, Fe(OAc)2, FeSO4·7H2O, or FeCl2·4H2O may be used. For Ni, Ni(NO3)2·6H2O, NiCl2·2H2O, Ni(CO)4, or Ni(OAc)2·4H2O may be used. When the above-mentioned main catalyst precursor is used, there is an advantage that the loss of the main catalyst component can be minimized during the subsequent drying and calcination processes, and a catalyst having high activity can be produced.

[0040] The promoter component may be one or more selected from the group consisting of Mo and V, and preferably V. The promoter component plays a role in increasing the dispersion of the main catalyst component to further enhance the activity of the catalyst, and the promoter component described above has the advantage of having a high synergistic effect with the promoter component described above and being easily supported on a support.

[0041] The promoter component may also be contained in the catalyst support liquid in the form of a precursor. Specifically, the promoter precursor may include a halide, nitride, oxide, nitrate, sulfate, sulfide, hydroxide, or metal salt of the promoter component. More specifically, in the case of Mo, (NH4)6Mo7O 24 For V, NH4VO3, NaVO3, V(CO)6, V2SO4·7H2O, V2O3 or V2O5 can be used. The above-mentioned precursors have the advantage of being relatively easy to obtain and can be easily converted into the oxide form.

[0042] The solvent of the catalyst support liquid may be any solvent that can dissolve the main catalyst precursor and the co-catalyst precursor and can be easily removed by a subsequent drying process. Examples of the solvent that can be used include, but are not limited to, water, alcohol solvents such as ethanol, methanol, or butanol, and aromatic hydrocarbon solvents such as toluene or xylene.

[0043] The molar ratio of the main catalyst component to the co-catalyst component in the catalyst support liquid may be 10:0.1 to 10:10, preferably 10:0.5 to 10:5. When the molar ratio of the main catalyst component to the co-catalyst component satisfies the above conditions, the synergistic effect between the two components can be maximized, specifically, the entanglement of the active component in the support can be minimized and the activity of the catalyst can be maximized.

[0044] The concentration of the main catalyst component in the catalyst-supporting liquid may be 2 to 15 wt%, preferably 3 to 10 wt%, and the concentration of the promoter component may be 0.1 to 1.5 wt%, preferably 0.3 to 1.0 wt%. When the concentrations of each component in the catalyst-supporting liquid are within the above ranges, the main catalyst and promoter components can be more easily supported.

[0045] In addition to the main catalyst precursor and the co-catalyst precursor, the catalyst support solution may further contain an organic acid. The organic acid used in the present invention may be, for example, a multicarboxylic acid, which is a compound containing one or more carboxyl groups. It has high solubility as a complexing agent, suppresses precipitation, facilitates catalyst synthesis, and acts as an activator to enhance carbon nanotube synthesis. The multicarboxylic acid may be one or more selected from dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids, such as citric acid, oxalic acid, malonic acid, succinic acid, or tartaric acid.

[0046] The organic acid may be contained in an amount of 0.1 to 1.5 wt % based on the total weight of the catalyst-supporting solution. Within this range, precipitation of the metal components of the main catalyst and co-catalyst in the catalyst solution does not occur, and cracking during the subsequent calcination process can also be suppressed.

[0047] In addition, the molar ratio of the sum of the main catalyst precursor and the co-catalyst precursor to the organic acid can be appropriately mixed in the range of about 5:1 to 30:1, and when such a molar ratio is satisfied, the bulk density of carbon nanotubes synthesized from the produced supported catalyst can be further increased.

[0048] Mixing step (S1) In order to support the main catalyst and co-catalyst components in the catalyst support solution on the support, a step of mixing the catalyst support solution with the support is first performed. This mixing process is commonly applied in catalyst manufacturing methods using a support method, but in the present invention, unlike conventional methods, pressure is applied during the mixing process, allowing more catalyst components to be introduced into the support.

[0049] Specifically, in the catalyst production method of the present invention, the mixing step is carried out under a pressure of 1.5 to 4.5 bar, preferably 2 to 4 bar. When mixing is carried out under the above pressure conditions, the catalyst components introduced into the support can be maximized. If the pressure is lower than the above range, the effect of pressurization is not significant. If the pressure is higher than the above range, the energy required for pressurization increases, reducing economic efficiency and the mixing equipment may not be able to withstand the pressurization.

[0050] Conditions other than the above pressure conditions may be applied without any particular limitation to those that can be applied to the mixing process.

[0051] Meanwhile, in this step, the support and the catalyst-supported liquid may be mixed so that the content of the main catalyst component is 1 to 30 wt%, preferably 3 to 20 wt%, and more preferably 5 to 15 wt% of the total weight of the catalyst. When the content of the main catalyst component is within the above range, the catalytic activity can be maximized.

[0052] Drying step (S2) In order to efficiently convert the main catalyst and co-catalyst precursors of the mixed catalyst support liquid into oxide forms, a drying step is required to first remove the solvent from the mixture before the calcination step.

[0053] The drying in this step can be carried out using equipment commonly used for drying, and can be carried out under atmospheric pressure or reduced pressure. When drying is carried out under atmospheric pressure, it can be carried out using equipment such as an oven, and when drying is carried out under reduced pressure, it can be carried out using equipment such as a dryer equipped with a reduced pressure device. When drying is carried out under reduced pressure, the pressure can be 10 to 100 mbar, preferably 50 to 100 mbar. When drying is carried out under reduced pressure within the above pressure range, there is an advantage that a larger amount of solvent can be removed.

[0054] The temperature at which drying is carried out may be 50 to 200°C, particularly 100 to 150°C in the case of drying at normal pressure, and 50 to 100°C in the case of drying under reduced pressure. Since drying is easier under reduced pressure conditions, the temperature in drying under reduced pressure may be lower than that in drying under normal pressure. Within the above temperature conditions, the solvent of the catalyst-supported liquid can be removed more smoothly; if the temperature is too low, the solvent may not be removed sufficiently, and if the temperature is too high, the solvent may be removed sufficiently, but problems such as loss of the catalyst component and the support may occur.

[0055] Firing step (S3) After the solvent has been thoroughly removed through the previous drying step, the dried mixture is calcined to obtain the final catalyst. During the calcination process, the main catalyst and co-catalyst precursor components on the surface and inside of the support are converted to oxides, which can then have catalytic activity.

[0056] The calcination may be carried out at a temperature of 600 to 800°C, preferably 650 to 750°C, for 0.5 to 3 hours, preferably 1 to 2 hours. If the calcination temperature in this step is too low or the calcination time is too short, the catalyst precursor may not be sufficiently converted into an oxide form. If the calcination temperature is too high or the calcination time is too long, the support may be structurally destroyed, or the supported co-catalyst and main catalyst components may fall off.

[0057] The content of the main catalyst component in the catalyst for producing carbon nanotubes prepared through these steps may be 5 to 20 wt%, preferably 10 to 15 wt%. The content of the main catalyst component may be calculated by dividing the mass of the main catalyst component in the main catalyst precursor added during the preparation process by the mass of the final catalyst obtained, or alternatively, by measuring the content of the main catalyst component in the catalyst particles using ICP-OES analysis.

[0058] Carbon nanotube manufacturing method The present invention provides a method for producing carbon nanotubes using a catalyst produced by the above-mentioned catalyst production method. Specifically, the present invention provides a method for producing carbon nanotubes, comprising the steps of (S1) mixing a catalyst support liquid with a support to obtain a mixture, (S2) drying the mixture, (S3) calcining the dried mixture to obtain a supported catalyst, (S4) introducing the obtained catalyst into a chemical vapor deposition reactor, and (S5) synthesizing carbon nanotubes by injecting a carbon source gas into the reactor and heating it, wherein step S1 is performed at 1.5 to 4.5 bar.

[0059] In the method for producing carbon nanotubes, steps S1 to S3 are the same as those described in the method for producing the catalyst.

[0060] Step S4 is a step of introducing the catalyst obtained through the previous step into a chemical vapor deposition reactor, and the introduced catalyst flows and synthesizes carbon nanotubes on its surface. The reactor used in this method is a chemical vapor deposition reactor, and any reactor generally used for synthesizing carbon nanotubes can be used without any special design restrictions. Meanwhile, in this step, a portion of pre-synthesized carbon nanotube particles may be introduced together with the catalyst to ensure the internal temperature of the reactor. When carbon nanotube particles are introduced together with the catalyst, a sufficient internal temperature of the reactor can be ensured even with a small amount of catalyst, which is advantageous in that a uniform reactor can be produced.

[0061] Meanwhile, in the production method of the present invention, the carbon source gas is a carbon-containing gas that can be decomposed at high temperatures to form carbon nanotubes. Specific examples of the carbon source gas that can be used include various carbon-containing compounds such as aliphatic alkanes, aliphatic alkenes, aliphatic alkynes, and aromatic compounds. More specific examples of the carbon source gas that can be used include 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, and acetaldehyde.

[0062] In the manufacturing method of the present invention, a fluidizing gas can be injected into the chemical vapor deposition reactor together with the carbon source gas. The fluidizing gas is used to impart fluidity to the carbon nanotubes and catalyst particles synthesized in the fluidized bed reactor. The fluidizing gas can be a gas that does not react with the carbon source gas or the carbon nanotubes and has high thermal stability. For example, nitrogen gas or an inert gas can be used as the fluidizing gas.

[0063] In the production method of the present invention, a reducing gas can be injected together with the carbon source gas and the fluidizing gas. The reducing gas can further promote the decomposition of the carbon source gas, and for example, hydrogen gas can be used as the reducing gas.

[0064] In the production method of the present invention, heating in the synthesis step can be performed so that the internal temperature of the reactor is 600 to 800°C. When the temperature in the reactor is within the above range, the carbon source gas is easily decomposed, and carbon nanotubes can be easily synthesized. If the temperature is outside the above range, carbon nanotubes cannot be produced well, and if the temperature is outside the above range, not only will heating be expensive but the catalyst particles themselves may decompose.

[0065] The carbon nanotubes produced by the method of producing carbon nanotubes provided by the present invention have a density of 20 kg / m 3 or more, preferably 23 kg / m 3 More than 24 kg / m, particularly preferably 3 It can exhibit a bulk density of 50 kg / m or more. 3 Less than 40 kg / m 3 The following bulk densities can be exhibited: Carbon nanotubes having a bulk density within the above range can have particularly excellent dispersibility and conductivity.

[0066] Hereinafter, the present invention will be described in detail with reference to examples and experimental examples in order to specifically explain the present invention. However, the present invention is not limited to these examples and experimental examples. The examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0067] Example 1 Specific surface area is 190m 2An alumina support with a % CO₂ / g and a D50 of 50 μm was prepared. A catalyst support solution was prepared by mixing and dissolving the cobalt precursor Co(NO3)2·6H2O and the vanadium precursor NH4VO3 in water at a molar ratio of 10:1. The cobalt concentration in the catalyst support solution was 8.4 wt% and the vanadium concentration was 0.7 wt%. The previously prepared alumina support was added to the prepared catalyst support solution and mixed until the cobalt content in the catalyst reached 13 wt%, while the pressure was maintained at 2 bar. After mixing was completed, the mixture was dried at atmospheric pressure and 120°C and then calcined in air at 720°C for 1 hour and 30 minutes to obtain a catalyst. In Table 1 below, "drying at atmospheric pressure" refers to drying under the same conditions as in Example 1.

[0068] Examples 2 to 7 The same procedure as in Example 1 was carried out, but the pressure during the mixing process, drying conditions, and cobalt content were varied as shown in Table 1 below to obtain catalysts. Meanwhile, in Table 1 below, "drying under reduced pressure" means drying was carried out under conditions of 80 mbar and 80°C.

[0069] Comparative Examples 1 to 4 The catalysts were obtained in the same manner as in Example 1 except that no pressure was applied during mixing, and the drying conditions and cobalt content were varied. The production conditions for each comparative example are summarized in Table 1 below.

[0070] [Table 1]

[0071] Experimental Example 1: Confirmation of the physical properties of carbon nanotubes produced from catalysts The catalysts prepared in the examples and comparative examples were placed in a chemical vapor deposition reactor, and nitrogen, hydrogen, and ethylene gases were added to the reactor in a volume ratio of 1:1:1. The temperature inside the reactor was then raised to 680°C to synthesize carbon nanotubes. The bulk density and yield of the obtained carbon nanotubes were measured and summarized in Table 2 below. The bulk density and yield were measured by the following methods.

[0072] 1) Bulk density: A 5 ml cylinder was filled with the prepared carbon nanotube powder, and the volume was measured by reading the scale. The weight of the carbon nanotubes measured by placing it on a scale was then divided by the previously measured volume to calculate the bulk density.

[0073] 2) Yield: Calculated according to the following formula. Yield = (total weight of produced carbon nanotubes - weight of catalyst used in production) / weight of catalyst used in production

[0074] [Table 2]

[0075] As can be seen from Table 2, the use of the catalysts of the Examples resulted in the production of carbon nanotubes with a higher bulk density than the use of the catalysts of the Comparative Examples. A higher bulk density of the produced carbon nanotubes means that a larger amount of carbon nanotubes was synthesized within the same reactor volume, demonstrating the superior carbon nanotube synthesis ability of the catalysts produced using the catalyst production method of the present invention. Furthermore, in terms of yield, which can be used to compare the amount of carbon nanotubes synthesized per catalyst used, the catalysts of the Examples generally exhibited a higher yield for the same cobalt content. Meanwhile, in Comparative Example 4, in which mixing was performed under higher pressure conditions than the Examples, the bulk density of the produced carbon nanotubes was higher than that of the Examples, but the yield itself was inferior to that of the Examples. This confirms that the synthesis of carbon nanotubes using a catalyst produced using the catalyst production method of the present invention can economically produce a large amount of carbon nanotubes.

Claims

1. A step (S1) of mixing a catalyst-supported liquid and a support to obtain a mixture; A step (S2) of drying the mixture; and (S3) calcining the dried mixture in air to obtain a supported catalyst; The S1 step is carried out at 2 bar to 4 bar, the catalyst-supporting liquid contains a Co precursor, the support is alumina; The method for producing a catalyst for producing carbon nanotubes, wherein the support has a specific surface area of ​​100 m 2 / g to 1000 m 2 / g.

2. 2. The method for producing a catalyst for producing carbon nanotubes according to claim 1, wherein the catalyst-supporting liquid contains a precursor of a promoter metal selected from the group consisting of Mo and V.

3. 3. The method for producing a catalyst for producing carbon nanotubes according to claim 2, wherein the molar ratio of the main catalyst metal precursor to the promoter catalyst metal precursor in the catalyst-supporting liquid is 5:1 to 20:

1.

4. The method for producing a catalyst for producing carbon nanotubes according to claim 1 , wherein the step S2 is carried out under atmospheric pressure or reduced pressure.

5. 2. The method of claim 1, wherein the step S2 is performed at 10 mbar to 100 mbar.

6. 2. The method for producing a catalyst for producing carbon nanotubes according to claim 1, wherein the step S2 is carried out at a temperature of 50 to 200.degree.

7. 2. The method of claim 1, wherein the step S3 is performed at a temperature of 600 to 800° C. for 0.5 to 3 hours.

8. A step (S1) of mixing a catalyst-supported liquid and a support to obtain a mixture; A step (S2) of drying the mixture; (S3) calcining the dried mixture in air to obtain a supported catalyst; (S4) introducing the obtained catalyst into a chemical vapor deposition reactor; and (S5) injecting a carbon source gas into the reactor and heating it to synthesize carbon nanotubes; The S1 step is carried out at 2 bar to 4 bar, the catalyst-supporting liquid contains a Co precursor, the support is alumina; The method for producing carbon nanotubes, wherein the support has a specific surface area of ​​100 m 2 / g to 1000 m 2 / g.

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