Supported catalyst for preparing carbon nanotube, carbon nanotube and preparation method thereof

Abstract

The supported catalyst for preparing carbon nanotubes according to the present invention comprises: a sheet-like support; and a plurality of metal catalyst particles attached to a surface of the sheet-like support and including cobalt and vanadium. The method for preparing carbon nanotubes according to the present invention comprises the steps of: preparing a mixture comprising a metal precursor and a polymer gel; calcining the mixture to prepare a flaky carrier; attaching a plurality of metal catalyst particles including cobalt and vanadium on a surface of the sheet-like support to prepare a supported catalyst; and contacting the supported catalyst with a carbon source to produce carbon nanotubes. The carbon nanotubes according to the present invention have an average straightness of 0.8 or more.

Description

Technical Field

[0001] The present invention provides a supported catalyst for preparing carbon nanotubes, carbon nanotubes, and a method for preparing the same. Background Art

[0002] Carbon nanotubes (CNT) have excellent chemical stability, mechanical and physical properties, and high thermal conductivity, and thus are materials used in many fields.

[0003] Carbon nanotubes are classified into single-walled carbon nanotubes having a structure formed by curling and connecting the ends of a single-layer graphite structure, double-walled carbon nanotubes having a form in which two single-layer carbon nanotubes form a concentric axis, multi-walled carbon nanotubes composed of multiple single walls, etc. according to synthesis conditions.

[0004] Since carbon nanotubes are composed of a graphite structure, free electrons can move along the surface of the carbon nanotubes, and the carbon nanotubes can have high conductivity. Therefore, carbon nanotubes can be applied to various fields requiring electrical properties such as antistatic, electromagnetic wave shielding, and heat dissipation. In particular, when individual carbon nanotubes are arranged or oriented in a certain direction, they can have higher conductivity, and the closer the shape of the carbon nanotubes is to a straight line, the higher the conductivity can be.

[0005] Carbon nanotubes also have high electrical attraction, and thus are usually obtained in an entangled type in which individual carbon nanotubes are entangled. Individual carbon nanotubes separated from the entangled carbon nanotubes can be zigzag-bent and have low conductivity. Therefore, there is a need for a method for preparing carbon nanotubes having high conductivity. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] One technical problem of the present invention is to provide a supported catalyst for preparing carbon nanotubes that can provide carbon nanotubes having improved quality.

[0008] One technical problem of the present invention is to provide carbon nanotubes having improved quality.

[0009] One technical problem of the present invention is to provide a method for preparing carbon nanotubes having improved quality.

[0010] (II) Technical Solutions

[0011] The supported catalyst for preparing carbon nanotubes according to the present invention includes: a flaky carrier; and a plurality of metal catalyst particles attached to the surface of the flaky carrier and containing cobalt and vanadium.

[0012] According to an exemplary embodiment, the flaky carrier may comprise alumina.

[0013] According to an exemplary embodiment, the thickness of the flaky carrier may be from 80 nm to 150 nm.

[0014] According to an exemplary embodiment, the average particle size (D50) of the flaky carrier may be from 15 μm to 30 μm.

[0015] According to an exemplary embodiment, the BET specific surface area of the flaky carrier may be 5 m 2 / g to 50 m 2 / g.

[0016] According to an exemplary embodiment, in the total weight of the supported catalyst, the content of the metal catalyst particles may be from 10% by weight to 30% by weight.

[0017] According to an exemplary embodiment, in the total moles of metals contained in the metal catalyst particles, the ratio of the content of vanadium to the content of cobalt may be more than 0 and 0.5 or less.

[0018] According to an exemplary embodiment, in the total moles of metals contained in the metal catalyst particles, the ratio of the content of vanadium to the content of cobalt may be from 0.05 to 0.25.

[0019] According to the method for preparing carbon nanotubes of the present invention, a mixture containing a metal precursor and a polymer gel is prepared. The mixture is calcined to prepare a flaky carrier. A plurality of metal catalyst particles containing cobalt and vanadium are attached to the surface of the flaky carrier to prepare a supported catalyst. The supported catalyst is contacted with a carbon source to prepare carbon nanotubes.

[0020] According to an exemplary embodiment, the calcination may be carried out at a temperature of 500 °C to 1000 °C.

[0021] According to an exemplary embodiment, the carbon source conversion rate may be from 50% to 90%, and the carbon source conversion rate is defined as the percentage of the total weight of the carbon nanotubes relative to the total weight of the carbon source.

[0022] The carbon nanotubes according to the present invention have an average straightness represented by the following formula 1 of 0.8 or more.

[0023] [Formula 1]

[0024]

[0025] In Formula 1, n is an integer from 10 to 100, and L kIt refers to the distance obtained by connecting two end points of any single carbon nanotube with a straight line in a scanning electron microscope (SEM) image of the carbon nanotube, V 总和(sum)，k It refers to the sum of the lengths of the two-dimensional vectors formed between the two end points of any single carbon nanotube in a scanning electron microscope (SEM) image, where 5 - 20 two-dimensional vectors are connected to each other along the shape of the single carbon nanotube.

[0026] According to an exemplary embodiment, the carbon nanotube may include at least one bent portion.

[0027] (III) Beneficial effects

[0028] The supported catalyst for preparing carbon nanotubes according to an exemplary embodiment of the present invention can provide carbon nanotubes having a shape similar to a straight line. Therefore, the orientation of the carbon nanotubes can be improved, and free electrons can smoothly move on the surface of the carbon nanotubes, thereby improving the conductivity of the carbon nanotubes.

[0029] The supported catalyst for preparing carbon nanotubes according to an exemplary embodiment of the present invention can provide high-purity carbon nanotubes in a high yield.

[0030] The carbon nanotubes according to an exemplary embodiment of the present invention have a shape similar to a straight line and thus can have high orientation. Description of the drawings

[0031] Figure 1 It is a schematic diagram of a cross-section of an exemplary supported catalyst for preparing carbon nanotubes.

[0032] Figure 2 It is a schematic flow chart of an exemplary method for preparing carbon nanotubes.

[0033] Figure 3 It is a particle size distribution diagram of the flaky carrier in the preparation example.

[0034] Figure 4 and Figure 5 It is an SEM image of the flaky carrier in Preparation Example 1.

[0035] Figure 6 It is an SEM image of the carbon nanotubes in Example 2.

[0036] Figure 7a is Figure 6 an enlarged view of the dotted-line marked part.

[0037] Figure 7b It is for explaining Figure 7a the calculation method of the straightness of the carbon nanotubes. Detailed implementation manners

[0038] The present invention provides a supported catalyst for preparing carbon nanotubes, which comprises a platelet-shaped carrier. In addition, the present invention provides a method for preparing carbon nanotubes by using the supported catalyst for preparing carbon nanotubes and the carbon nanotubes prepared thereby.

[0039] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, this is merely an exemplary description, and the present invention is not limited to the specific embodiments described exemplarily.

[0040] Figure 1 is a schematic cross-sectional view of an exemplary supported catalyst for preparing carbon nanotubes. Referring to Figure 1 , the supported catalyst 100 for preparing carbon nanotubes comprises a platelet-shaped carrier 10 and a plurality of metal catalyst particles 20.

[0041] The platelet-shaped carrier 10 may have dimensions in the length and width directions that are longer than the dimension in the thickness direction. The thickness direction may be a direction perpendicular to the length and width directions. Therefore, the platelet-shaped carrier 10 may have a platelet shape.

[0042] In an exemplary embodiment, the thickness of the platelet-shaped carrier 10 may be 80 nm to 150 nm. In addition, the longer of the lengths in the length and width directions of the platelet-shaped carrier 10 may be 15 μm to 30 μm.

[0043] According to an exemplary embodiment, the average particle size (D50) of the platelet-shaped carrier 10 may be 15 μm to 30 μm. According to some embodiments, the average particle size (D50) of the platelet-shaped carrier 10 may be 20 μm to 28 μm.

[0044] The particle size of the platelet-shaped carrier may refer to the maximum size on the plane defined by the length and width directions of the platelet-shaped carrier. The average particle size (D50) refers to the particle size when the cumulative volume distribution percentage of the particles reaches 50%. The cumulative volume distribution can be obtained using, for example, a laser particle size analyzer (e.g., LA-950V2 / Horiba).

[0045] In an exemplary embodiment, the average value of the area of the platelet-shaped carrier 10 divided by the thickness may be 3000 μm to 7000 μm. In some embodiments, the average value of the area of the platelet-shaped carrier 10 divided by the thickness may be 4000 μm to 6500 μm. The "area" may refer to the area of the platelet-shaped carrier 10 defined by the length and width directions.

[0046] According to an exemplary embodiment, the BET specific surface area of the platelet-shaped carrier 10 may be 5 m 2 / g to 50 m 2 / g. According to some embodiments, the BET specific surface area of the flaky support 10 can be 5 m 2 / g to 25 m 2 / g. The BET specific surface area may refer to the nitrogen adsorption surface area measured by the Brunauer - Emmett - Teller (BET) method. The measurement method of the BET specific surface area is not particularly limited, but it can be measured using, for example, Micromeritics / 3Flex.

[0047] For example, the BET specific surface area can be measured by the following method. 0.1 g of the flaky support can be filled in the BET cell, and then heated to 150 °C under vacuum to remove moisture. The weight of the flaky support after removing moisture can be measured, and then while injecting nitrogen, the amount of nitrogen adsorbed on the sample can be measured. After stopping the nitrogen injection, the inside of the BET cell can be made vacuum again to measure the amount of nitrogen desorbed from the sample, whereby the BET specific surface area of the flaky support can be calculated.

[0048] The flaky support 10 having a BET specific surface area within the above range can have a surface area with a width suitable for the attachment of the metal catalyst particles 20.

[0049] In an exemplary embodiment, the flaky support 10 may contain a metal oxide. The metal oxide may be a ceramic component that does not react with the carbon source. For example, the metal oxide may contain alumina.

[0050] The metal catalyst particles 20 contain cobalt (Co) and vanadium (V). Cobalt can act as the main catalyst for the reaction of converting the carbon source into carbon nanotubes, and vanadium can act as a co - catalyst to assist the function of cobalt as the main catalyst.

[0051] In addition to cobalt and vanadium, the metal catalyst particles 20 may further contain other metals. For example, the metal catalyst particles 20 may further contain iron, nickel, etc.

[0052] According to an exemplary embodiment, in the total molar amount of metals contained in the metal catalyst particles 20, the ratio of the content of vanadium to the content of cobalt can be more than 0 and 0.5 or less. According to some embodiments, in the total molar amount of metals contained in the metal catalyst particles 20, the ratio of the content of vanadium to the content of cobalt can be 0.05 to 0.25 or 0.1 to 0.25.

[0053] Within the above range, carbon nanotubes with higher purity and a shape closer to a straight line can be prepared.

[0054] According to an exemplary embodiment, the content of the metal catalyst particles 20 in the total weight of the supported catalyst 100 may be 10% by weight to 30% by weight. According to some embodiments, the content of the metal catalyst particles 20 in the total weight of the supported catalyst 100 may be 10% by weight to 25% by weight or 15% by weight to 20% by weight.

[0055] Within the above ranges, carbon nanotubes with higher purity and a shape closer to a straight line can be prepared.

[0056] According to an exemplary embodiment, the average particle size (D50) of the metal catalyst particles 20 may be 50 nm to 150 nm. According to some embodiments, the average particle size (D50) of the metal catalyst particles 20 may be 80 nm to 120 nm. Within the above ranges, carbon nanotubes with a sufficient number of surface active sites for carbon nanotube growth and an appropriate length can be prepared.

[0057] According to the present invention, a method for preparing carbon nanotubes is provided. Figure 2 is a schematic flowchart of an exemplary method for preparing carbon nanotubes. Hereinafter, with reference to the accompanying drawings, each step of the method will be described in detail.

[0058] First, a mixture containing a metal precursor and a polymer gel (e.g., Figure 2 S10) is prepared. The metal precursor may be a compound of the metal contained in the metal oxide of the flaky carrier. The polymer gel may act as a template to enable the metal precursor to be formed into a flaky shape.

[0059] The metal precursor may include, for example, metal nitrates, metal hydroxides, metal sulfides, etc. For example, the metal precursor may be an aluminum precursor. For example, the aluminum precursor may be aluminum nitrate.

[0060] The polymer gel may be a polymer hydrogel. For example, the polymer gel may be prepared by mixing a hydrophilic polymer and water. The hydrophilic polymer may include, for example, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyethylene glycol, polyvinyl pyrrolidone, polyacrylonitrile, polytetrafluoroethylene, ethylene glycol, and diethylene glycol, etc., and these may be used alone or in combination of two or more.

[0061] In an exemplary embodiment, the polymer gel may be prepared by mixing 300 - 1000 parts by weight of water with respect to 100 parts by weight of the hydrophilic polymer. In this case, the mixing may be carried out at a temperature of about 80°C to 95°C.

[0062] In an exemplary embodiment, the content of the metal precursor may be 30 parts by weight to 70 parts by weight relative to 100 parts by weight of the polymer gel.

[0063] The mixture comprising the metal precursor and the polymer gel may further comprise other components. For example, the mixture may further comprise water to dissolve the metal precursor, and may further comprise a compound that enables the metal oxide formed from the metal precursor to have an appropriate surface area, porosity, and low density.

[0064] The compound may comprise, for example, glycine, proline, glutamic acid, serine, theanine, methionine, valine, leucine, L-aspartic acid, glutathione, etc., and these may be used alone or in combination of two or more.

[0065] Next, the mixture is calcined to prepare a flaky support (e.g., Figure 2 S20). Through the calcination, the polymer gel as an organic component can be removed while forming the flaky support.

[0066] According to an exemplary embodiment, the mixture may be placed in a heating furnace and heated at a heating rate of about 2 - 10 °C / minute, and when the calcination temperature is reached, the temperature is maintained for calcination.

[0067] According to an exemplary embodiment, the calcination may be carried out at a temperature of 500 °C to 1000 °C. According to some embodiments, the calcination may be carried out at a temperature of 600 °C to 900 °C or 700 °C to 850 °C. Within the above range, a flaky support with an appropriate thickness can be formed.

[0068] The calcination may be carried out for about 3 hours to 10 hours or 4 hours to 6 hours, and may be carried out in an air atmosphere. Thus, a flaky support containing a metal oxide can be formed.

[0069] Next, a plurality of metal catalyst particles are attached to the surface of the flaky support to prepare a supported catalyst (e.g., Figure 2 S30). The metal catalyst particles contain cobalt and vanadium, and the detailed content of the metal catalyst particles may be the same as that described above.

[0070] According to an exemplary embodiment, the flaky support and the plurality of metal catalyst particles may be mixed and then calcined to prepare a supported catalyst. For example, the calcination may be carried out at a temperature of 500 °C to 1000 °C.

[0071] Next, the supported catalyst is contacted with a carbon source to prepare carbon nanotubes (e.g., Figure 2of S40). The preparation can be carried out in a batch reactor or a continuous reactor.

[0072] For example, the supported catalyst can be added into the interior of a batch reactor, and a mixed gas containing a carbon source can be injected into the interior of the reactor to prepare carbon nanotubes. The carbon source can be a gaseous hydrocarbon, and the mixed gas can contain the carbon source and hydrogen. There is no particular limitation on the mixing ratio of the carbon source and hydrogen, but for example, the volume ratio can be from 25:75 to 75:25.

[0073] According to an exemplary embodiment, the supported catalyst can be reacted with the carbon source at a temperature of about 500 °C to 1000 °C for 10 minutes to 100 minutes to prepare carbon nanotubes.

[0074] According to an exemplary embodiment, the carbon source conversion rate can be 50% to 90%, and the carbon source conversion rate is defined as the percentage of the total weight of the carbon nanotubes relative to the total weight of the carbon source. According to some embodiments, the carbon source conversion rate can be 60% to 90%, and the carbon source conversion rate is defined as the percentage of the total weight of the carbon nanotubes relative to the total weight of the carbon source. The higher the carbon source conversion rate, the more the productivity of the carbon nanotubes can be improved.

[0075] According to an exemplary embodiment, the carbon nanotube production efficiency of the supported catalyst for preparing carbon nanotubes can be 10 g CNT / g 催化剂 to 32 g CNT / g 催化剂 . According to some embodiments, the carbon nanotube production efficiency of the supported catalyst for preparing carbon nanotubes can be 25 g CNT / g 催化剂 to 32 g CNT / g 催化剂 .

[0076] The carbon nanotube production efficiency can be defined as the ratio of the total weight of the carbon nanotubes to the total weight of the supported catalyst. For example, when the addition amount of the supported catalyst is about 1 g and the yield of the carbon nanotubes is about 15 g, the carbon nanotube production efficiency of the supported catalyst can be about 15 g CNT / g 催化剂 .

[0077] For example, the production efficiency can be calculated based on the weight of the carbon nanotubes obtained when using 1 g of the supported catalyst, adding about 37.5 g of the carbon source, and reacting at a temperature of about 700 °C.

[0078] The carbon nanotubes according to the present invention have an average straightness of 0.8 or more represented by the following formula 1.

[0079] [Formula 1]

[0080]

[0081] In Formula 1, n is an integer from 10 to 100, and L k refers to the distance obtained by connecting two endpoints of any single carbon nanotube with a straight line in the SEM image of the carbon nanotube, and V 总和，k refers to the sum of the lengths of the 5 - 20 two - dimensional vectors formed between the two endpoints of the any single carbon nanotube in the SEM image and connected to each other along the shape of the single carbon nanotube.

[0082] The "average straightness" can be the average of the straightness of multiple single carbon nanotubes. The straightness can be a measure representing the degree of similarity between the carbon nanotube and a straight - line shape. The straightness can be expressed as the ratio of the length (L k ) when the carbon nanotube is in a straight - line shape to the value (V 总和，k ) approximating the actual length of the carbon nanotube.

[0083] The length when the carbon nanotube is in a straight - line shape can be measured as the shortest distance between the two endpoints of the carbon nanotube observed from the scanning electron microscope (SEM) image of the carbon nanotube. For example, it is the length of the straight line formed by connecting the two endpoints of the carbon nanotube.

[0084] The value approximating the actual length of the carbon nanotube can refer to the sum of the lengths of the 5 - 20 two - dimensional vectors formed between the two endpoints of the carbon nanotube in the SEM image and connected to each other along the shape. The two - dimensional vectors can be connected starting from one endpoint of the carbon nanotube and reaching the other endpoint. For example, in the two - dimensional vectors, the starting point of any vector can be the same as one endpoint of the carbon nanotube or the end point of another vector, and the end point of any vector can be the same as the other endpoint of the carbon nanotube or the starting point of another vector.

[0085] In addition, the two - dimensional vector can be a linear vector with direction and magnitude values, and the straightness can be calculated by taking the sum of the magnitude values as the value approximating the actual length of the carbon nanotube.

[0086] The number of the two - dimensional vectors can be adjusted between 5 and 20, and its number and length can vary according to the shape of the carbon nanotube. For example, the carbon nanotube can contain at least one bent portion. When the bending radius of the bent portion is small, the number of the two - dimensional vectors can increase, and the length can decrease. For example, the length of the two - dimensional vector can be from 1 nm to 1000 nm.

[0087] Therefore, the closer the shape of the carbon nanotube is to a straight line shape, the closer the straightness can be to a value of 1. When the shape of the carbon nanotube is a straight line shape, the straightness can be 1. For example, the straightness of any carbon nanotube can be 0.6 or more, and the average value of the straightness can be 0.8 or more.

[0088] The average straightness can be the average of the straightness values of 10 to 100 carbon nanotubes. For example, n can be 10 to 100 or 20 to 70.

[0089] According to an exemplary embodiment, the average straightness of the carbon nanotube can be 0.85 or more, 0.86 or more, 0.87 or more, 0.9 or more, 0.91 or more, 0.92 or more, 0.95 or more, or 0.96 or more, and can be 1 or less.

[0090] According to an exemplary embodiment, the carbon nanotube can include at least one bent portion. For example, the carbon nanotube can include 1 to 10 bent portions. The "bent portion" can refer to a region where the carbon nanotube extends from one point and bends along a rotational direction until another point. When the rotational direction changes, it can be defined as a different bent portion.

[0091] According to an exemplary embodiment, the length of the carbon nanotube can be about 3 μm to 12 μm.

[0092] Hereinafter, with reference to specific experimental examples, the embodiments of the present invention will be further described. The examples and comparative examples included in the experimental examples are only for illustrating the present invention and not for limiting the scope of rights. Various changes and modifications can be made to the examples within the scope and technical idea of the present invention, which will be obvious to those skilled in the art, and such variations and modifications also belong to the scope of rights.

[0093] Preparation Example 1

[0094] 8 g of polyvinyl alcohol (Sigma-Aldrich) and 40 g of deionized water were stirred and mixed at 90 °C for 30 minutes to prepare a polyvinyl alcohol gel. 21 g of anhydrous aluminum nitrate, 7 g of glycine, and 12 g of deionized water were stirred for 30 minutes to prepare an aluminum precursor solution. The aluminum precursor solution was slowly added to the polyvinyl alcohol gel, and then stirred for 30 minutes to prepare a mixture.

[0095] The mixture was placed in a muffle furnace, air was introduced at a flow rate of 2 L / minute, the temperature was raised at a rate of 5 °C / minute, and after reaching a temperature of 600 °C, it was calcined for 5 hours to prepare a flaky carrier.

[0096] Preparation Example 2

[0097] A flaky carrier was prepared by the same method as in Preparation Example 1, except that the calcination temperature was changed to 700 °C.

[0098] Preparation Example 3

[0099] A flaky carrier was prepared by the same method as in Preparation Example 1, except that the calcination temperature was changed to 800 °C.

[0100] Preparation Example 4

[0101] A flaky carrier was prepared by the same method as in Preparation Example 1, except that the calcination temperature was changed to 900 °C.

[0102] Experimental Example: Analysis of the Shape and Size of the Flaky Carrier

[0103] The particle size of the flaky carrier of the preparation example was analyzed using a laser particle size analyzer (Horiba / LA-950V2). Figure 3 The particle size distribution diagram of the flaky carrier of the preparation example is shown. The particle size distribution diagram is represented by the volume-based frequency according to the particle diameter (the maximum size in the plane direction). In addition, the average particle diameter (D50) of the flaky carrier of the preparation example measured using the particle size analyzer is shown in Table 1 below.

[0104] Scanning electron microscope (SEM) images of the flaky carrier of the preparation example were taken, the thickness of about 50 arbitrary individual flaky carriers was measured, and the average thickness was calculated. Figure 4 and Figure 5 The SEM image of the flaky carrier of Preparation Example 1 is shown. Specifically, Figure 5 is the SEM image of the flaky carrier of Preparation Example 1 taken at a higher magnification than Figure 4 .

[0105] As Figure 5 shown, the thickness of arbitrary flaky carrier particles was measured, and the thickness of about 50 particles was repeatedly measured by the same method, and the average thickness of the flaky carrier of the preparation example was calculated and shown in Table 1.

[0106] In addition, the BET specific surface area of the flaky carrier of the preparation example was measured using a BET measurement device (Micromeritics / 3Flex) and shown in Table 1.

[0107] [Table 1]

[0108]

[0109] Example 1

[0110] (1) Preparation of the Supported Catalyst

[0111] Dissolve a cobalt precursor and a vanadium precursor in distilled water to meet a molar ratio of 80 mol% cobalt and 20 mol% vanadium, thereby preparing a solution. Add the flaky carrier of Preparation Example 1 to the solution and calcine at 500 °C to prepare a supported catalyst containing metal catalyst particles. In the total weight of the supported catalyst, the content of the metal catalyst particles is 16% by weight.

[0112] (2) Preparation of carbon nanotubes

[0113] Add 1 g of the supported catalyst to a tubular furnace and add a mixed gas containing ethylene and hydrogen in a volume ratio of 1:1 at a rate of 2 liters (Lit.) / minute, and react at a temperature of 700 °C for 30 minutes to obtain about 24.8 g of carbon nanotubes. The total weight of ethylene added during the 30 minutes is 37.5 g.

[0114] Example 2

[0115] Prepare a supported catalyst and carbon nanotubes by the same method as in Example 1, except that when preparing the supported catalyst, use the flaky carrier of Preparation Example 2. At this time, the yield of carbon nanotubes is about 31.1 g.

[0116] Example 3

[0117] Prepare a supported catalyst and carbon nanotubes by the same method as in Example 1, except that when preparing the supported catalyst, use the flaky carrier of Preparation Example 3. At this time, the yield of carbon nanotubes is about 20.7 g.

[0118] Example 4

[0119] Prepare a supported catalyst and carbon nanotubes by the same method as in Example 1, except that when preparing the supported catalyst, use the flaky carrier of Preparation Example 4. At this time, the yield of carbon nanotubes is about 22.2 g.

[0120] Example 5

[0121] Prepare a supported catalyst and carbon nanotubes by the same method as in Example 2, except that when preparing the supported catalyst, make the content of the metal catalyst particles in the total weight of the supported catalyst 20% by weight. At this time, the yield of carbon nanotubes is about 27.2 g.

[0122] Example 6

[0123] Prepare a supported catalyst and carbon nanotubes by the same method as in Example 2, except that when preparing the supported catalyst, make the content of the metal catalyst particles in the total weight of the supported catalyst 24% by weight. At this time, the yield of carbon nanotubes is about 28.0 g.

[0124] Example 7

[0125] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 2, except that the supported catalyst was prepared such that the content of the metal catalyst particles was 12 wt% in the total weight of the supported catalyst. At this time, the yield of carbon nanotubes was about 25.6 g.

[0126] Example 8

[0127] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 2, except that a cobalt precursor and a vanadium precursor were used such that a molar ratio of 70 mol% cobalt and 30 mol% vanadium was satisfied. At this time, the yield of carbon nanotubes was about 13.0 g.

[0128] Example 9

[0129] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 2, except that a cobalt precursor and a vanadium precursor were used such that a molar ratio of 85 mol% cobalt and 15 mol% vanadium was satisfied. At this time, the yield of carbon nanotubes was about 29.6 g.

[0130] Example 10

[0131] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 2, except that a cobalt precursor and a vanadium precursor were used such that a molar ratio of 90 mol% cobalt and 10 mol% vanadium was satisfied. At this time, the yield of carbon nanotubes was about 28.9 g.

[0132] Comparative Example 1

[0133] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 1, except that amorphous alumina particles (Puralox TH 100 / 150) were used as the carrier. At this time, the yield of carbon nanotubes was about 26.4 g.

[0134] Comparative Example 2

[0135] The supported catalyst and carbon nanotubes were prepared by the same method as in Example 5, except that amorphous alumina particles (Puralox TH 100 / 150) were used as the carrier. At this time, the yield of carbon nanotubes was about 24.6 g.

[0136] The types of carriers, the composition of the metal catalyst particles, the content of the metal catalyst particles in the supported catalyst, and the yield and the recovery rate of the carbon nanotubes of the Examples and Comparative Examples are shown in Table 2 below.

[0137] [Table 2]

[0138]

[0139] Experimental Example: Calculation and Evaluation of the Average Straightness of Carbon Nanotubes

[0140] Take SEM images of the carbon nanotubes of the Examples and Comparative Examples, and then calculate the straightness and average value of individual carbon nanotubes from the SEM images.

[0141] Figure 6 The SEM image of the carbon nanotubes of Example 2 is shown in Figure 7a shown in Figure 6 an enlarged view of the dotted-line marked part of Figure 7a is the SEM image of an arbitrary individual carbon nanotube.

[0142] Figure 7b is a schematic diagram for explaining Figure 7a the calculation method of the straightness of the carbon nanotubes of

[0143] Refer to Figure 6 , Figure 7a and Figure 7b , measure the length (L Figure 7b the solid line L) of the straight line connecting the two endpoints (T1 and T2) of an individual carbon nanotube from the SEM image k ). In addition, 7 intermediate points ( Figure 7b M1 to M7 of Figure 7b ) can be set between the two endpoints ( Figure 7b the dotted arrows) of an individual carbon nanotube. When connecting the points of T1-M1, M1-M2, M2-M3, M3-M4, M4-M5, M5-M6, M6-M7, and M7-T2 to form 8 vectors ( 总和，k ), calculate the straightness (L k / V 总和，k ) using the sum of the lengths of each vector (V 总和，k ). By the method described above, calculate the straightness of about 20 (in Equation 1, n = 20) individual carbon nanotubes, and calculate the average value according to Equation 1.

[0144] Repeat the measurement and calculation by the method described above, and show L k , V 总和，k , straightness, and average straightness of Example 2, Comparative Example 1, and Comparative Example 2 in Tables 3 to 5 below, respectively. In addition, calculate the average straightness of the remaining Examples and Comparative Examples by the same method and show it in Table 6.

[0145] [Table 3]

[0146]

[0147] [Table 4]

[0148]

[0149] [Table 5]

[0150]

[0151] [Table 6]

[0152]

[0153] Referring to Table 6, the carbon nanotubes of the examples have a high average straightness of 0.8 or more.

[0154] The carbon nanotubes of Comparative Example 1 and Comparative Example 2 were prepared by using a supported catalyst containing a spherical carrier. Therefore, carbon nanotubes with low straightness were obtained.

[0155] The above description is only an example of applying the principles of the present invention, and other configurations may also be included without departing from the scope of the present invention.

Claims

1. A supported catalyst for preparing carbon nanotubes, comprising: A flaky support; and A plurality of metal catalyst particles attached to the surface of the flaky support and containing cobalt and vanadium.

2. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, The flaky support contains alumina.

3. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, The thickness of the flaky support is 80 nm to 150 nm.

4. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, The average particle size D50 of the flaky support is 15 μm to 30 μm.

5. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, The BET specific surface area of the flaky carrier is 5 m 2 / g to 50 m 2 / g.

6. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, In the total weight of the supported catalyst, the content of the metal catalyst particles is 10 wt% to 30 wt%.

7. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, In the total molar amount of the metal catalyst particles, the ratio of the content of vanadium to the content of cobalt is more than 0 and 0.5 or less.

8. The supported catalyst for preparing carbon nanotubes according to claim 1, wherein, In the total molar amount of the metal catalyst particles, the ratio of the content of vanadium to the content of cobalt is 0.05 to 0.

25.

9. A method for preparing carbon nanotubes, comprising the following steps: Preparing a mixture containing a metal precursor and a polymer gel; Calcining the mixture to prepare a flaky support; Attaching a plurality of metal catalyst particles containing cobalt and vanadium to the surface of the flaky support to prepare a supported catalyst; And Bringing the supported catalyst into contact with a carbon source to prepare carbon nanotubes.

10. The method for preparing carbon nanotubes according to claim 9, wherein, The calcination is carried out at a temperature of 500 °C to 1000 °C.

11. The method for preparing carbon nanotubes according to claim 9, wherein, The carbon source conversion rate is 50% to 90%, and the carbon source conversion rate is defined as the percentage of the total weight of the carbon nanotubes relative to the total weight of the carbon source.

12. A carbon nanotube having an average straightness represented by the following formula 1 of 0.8 or more: [Formula 1] In Formula 1, n is an integer from 10 to 100, L k is the distance obtained by connecting two end points of any single carbon nanotube with a straight line in a scanning electron microscope image of the carbon nanotube, and V 总和，k is the sum of the lengths of the two-dimensional vectors when 5-20 two-dimensional vectors that are connected to each other along the shape of the single carbon nanotube are formed between the two end points of the arbitrary single carbon nanotube in the scanning electron microscope image.

13. The carbon nanotube according to claim 12, wherein, The carbon nanotube has at least one bent portion.

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