WO2018074652A1

WO2018074652A1 - Catalyst and continuous process for mass production of multi-walled carbon nanotube

Info

Publication number: WO2018074652A1
Application number: PCT/KR2016/013114
Authority: WO
Inventors: Sang Hyo Ryu; Hyun Kyung Sung; Chung Heon Jeong; Dong Hwan Kim
Original assignee: Korea Kumho Petrochemical Co., Ltd.
Priority date: 2016-10-17
Filing date: 2016-11-15
Publication date: 2018-04-26
Also published as: CN107954413A; KR20180041878A; JP2018065122A; KR101876293B1; JP6357215B2

Abstract

The present invention relates to a catalyst and a continuous process for mass production of multi-walled carbon nanotube. More particularly, it relates to a catalyst for mass production of multi-walled carbon nanotube as well as a continuous process for the mass production of multi-walled carbon nanotube.

Description

CATALYST AND CONTINUOUS PROCESS FOR MASS PRODUCTION OF MULTI-WALLED CARBON NANOTUBE

Carbon nanotube has been first discovered by Dr. Sumio Iijima in 1991, which has a hexagonal honey comb structure connecting 1 carbon atom with 3 other neighboring carbon atoms, and the hexagonal structures are repeated and rolled in a cylinder or tube form. Of course, carbon nanotube is an extremely small material in which the fibrous diameter is a few nanometer levels. Further, carbon nanotube has been regarded as future promising new material, because it has excellent mechanical properties, excellent electrical conductivity, excellent field emission properties and/or excellent hydrogen storage medium. Therefore, it has been expected that carbon nanotube will be applied to aerospace material, biotechnology, environmental energy material, medicine and therapeutics and/or electronic computer in the near future.

For manufacturing the carbon nanotube in a large scale, the mass production process for synthesizing the carbon nanotube using the optimal catalyst has been researched.

For manufacturing the carbon nanotube in a large scale, it requires 2 processes which are a catalyst manufacturing process and a carbon nanotube manufacturing process. Further, these 2 processes can be designed in a continuous process or a separate process. However, in case of a separate process, the catalytic activity can be slightly declined according to the interval of time between 2 processes.

Further, any physical changes, such as, the agglomeration and/or the degradation among metal elements in the catalyst can occur to the catalyst composition for manufacturing carbon nanotube according to the lapse of time. Further, the catalytic activity in the high temperature can be also declined with the lapse of time. Therefore, it has been required that the catalyst for manufacturing carbon nanotube has to be supplied to the carbon nanotube manufacturing process without interval of time.

Therefore, it has been desirous that a catalyst manufacturing process and a carbon nanotube manufacturing process shall be designed to be one continuous manufacturing process.

As a main catalytic metal for producing carbon nanotube, iron (Fe), cobalt (Co) and/or nickel (Ni) has been already known. Further, chromium (Cr), manganese (Mn), molybdenum (Mo), vanadium (V), tungsten (W), tin (Sn), palladium (Pd) and/or copper (Cu) has been also known as a co-catalytic metal for producing carbon nanotube. Recently, an inactive support has been included in the catalyst composition for enhancing the catalytic activity.

In PCT International Publication No. WO2010/047439 A1 'Supported catalyst for synthesizing carbon nanotubes, method for preparing thereof and carbon nanotube using the same’, a supported catalyst for synthesizing carbon nanotubes, comprising i) Co, Fe and/or Ni metal catalysts; and ii) an inactive support selected from alumina, magnesium oxide and/or silica; has been disclosed.

Further, in this disclosure, molybdenum (Mo) has been introduced as an activator for enhancing the catalytic activity in the catalyst composition. The role of molybdenum has enhanced the thermal stability of catalytic metal (Fe, Co, Ni) and inactive support (Al, Mg, Si) to avoid the agglomeration and/or the degradation of catalytic metal and inactive support during the calcination of catalyst powder at 500~600℃ for about 0.5 hour. However, molybdenum (Mo) has been introduced as a selective component, which has not been necessarily required in the catalyst composition.

On the other hand, the inventors of present application have already developed a number of catalyst compositions for producing multi-walled carbon nanotube as follows.

In U.S. Pat. No. 8,048,821 ‘Catalyst composition for the synthesis of thin multi-walled carbon nanotube and its manufacturing method’, a catalyst composition for producing carbon nanotube represented by following formula [Fe_a:Al_b]_x:M_y:Mg_z wherein Fe represents catalytic metal of iron, its oxide; Al represents catalytic metal of aluminum, its oxide; Mg represents inactive support of magnesium, its oxide; M represents at least one transition metal selected from Co, Ni, Cr, Mn, Mo, W, V, Sn, or Cu, its oxide; x, y, and z represent molar fraction of [the sum of Fe and Al], M, and Mg, x+y+z=10, 2.0≤x≤8.0, 0.0≤y≤2.5, 0.5≤z≤8.0 a and b represent molar fraction of Fe and Al, a+b=10, 2.0≤a≤5.5, 4.5≤b≤8.0 has been disclosed.

In U.S. Pat. No. 8,673,807 ‘Catalyst composition for the synthesis of thin multi-walled carbon nanotube’, a catalyst composition for synthesis of carbon nanotube represented by following formula: [Co_a:Al_b]_x:M_y:Mg_z wherein Co represents catalytic metal of cobalt, its oxide, or its derivative; Al represents catalytic metal of aluminum, its oxide, or its derivative; Mg represents inactive support of magnesium, its oxide, or its derivative; M represents at least one transition metal selected from Ni, Cr, Mn, Mo, W, Pb, Ti, Sn, or Cu, its oxide, or its derivative; x, y, and z represent molar fraction of [the sum of Co and Al], M, and Mg, x+y+z=10, 2.0<x<9.9, 0.0<y<2.5, 0.1<z<8.0; a and b represent molar fraction of Co and Al, a+b=10, 4.0<a<8.0, 2.0<b<6.0 has been disclosed.

In U.S. Pat. No. 9,186,656 ‘Catalyst composition for the synthesis of multi-walled carbon nanotubes’, a catalyst composition for producing carbon nanotube represented by the following formula: [Fe_a:Mo_b]_x:M_y:Al_z wherein Fe, Mo represents catalyst active material of iron, molybdenum, its oxide, or its derivative; Al represents inactive support material of aluminum, its oxide, or its derivative; M represents at least one transition metal selected from the group consisting of Co, Ni, Ti, Mn, W, Sn, Cu, and oxides, or derivatives thereof; x, y, and z represent molar fraction of [the sum of Fe and Mo], M and Al, x+y+z=10, 1.0≤x≤4.0, 0.1≤y≤3.0, 2.5≤z≤8.0; and a and b represent molar fraction of Fe and Mo, a+b=10, 7.9≤a≤9.9, 0.1≤b≤2.1 has been disclosed.

Further, the essential component of catalyst composition for preparing multi-walled carbon nanotube can be briefly summarized as follows. In the U.S. Pat. No. 8,048,821, Fe and Al have been regarded as essential component. In the U.S. Pat. No. 8,673,807, Co and Al have been regarded as essential component. In the U.S. Pat. No. 9,186,656, Fe and Mo have been regarded as essential component.

Therefore, the optimal component of catalyst composition can be predicted as Fe, Co, Mo, Al in view of our previous U.S. Patent disclosures. Therefore, main catalyst (Fe, Co), co-catalyst (Mo) and inactive support (Al) can be inferred from above disclosures as optimal combination of catalytic metal and inactive support.

On the basis of inferred catalyst composition comprising main catalyst (Fe, Co), co-catalyst (Mo) and inactive support (Al), the inventors of present application have found a catalyst and a continuous process for mass production of multi-walled carbon nanotube, which comprises i) preparing the catalyst composition for manufacturing the multi-walled carbon nanotube by spray pyrolysis method, ii) manufacturing the multi-walled carbon nanotube by thermal chemical vapor deposition method in a fluidized bed reactor, and iii) collecting and obtaining the manufactured multi-walled carbon nanotube, wherein the fibrous diameter is 5~15nm, the apparent density is 0.02~0.1 g/cc and the catalytic yield (%) of multi-walled carbon nanotube is 1,400~3,000 %.

The problem to be solved of present invention is to develop a catalyst and a continuous process for mass production of multi-walled carbon nanotube, which comprises i) preparing the catalyst composition comprising main catalyst (Fe, Co), co-catalyst (Mo) and inactive support (Al) for manufacturing the multi-walled carbon nanotube by spray pyrolysis method, ii) manufacturing the multi-walled carbon nanotube by thermal chemical vapor deposition method in a fluidized bed reactor, and iii) collecting and obtaining the manufactured multi-walled carbon nanotube, wherein the fibrous diameter is 5~15nm, the apparent density is 0.02~0.1 g/cc and the synthetic yield (%) of catalyst is 1,400~3,000 %.

The object of the present invention is to provide a continuous process for mass production of multi-walled carbon nanotube comprising: 1) obtaining a catalyst composition for manufacturing multi-walled carbon nanotube according to spray pyrolysis method after dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water; 2) synthesizing the multi-walled carbon nanotube by thermal chemical vapor deposition of the carbon on the metal catalyst at 600~900℃ with supplying source gas and catalyst composition in a fluidized bed reactor; and 3) selecting and obtaining a multi-walled carbon nanotube manufactured in step 2), wherein said catalyst composition comprises the main catalyst (Fe, Co), the co-catalyst (Mo) and the inactive support (Al); and the synthetic yield (%) of catalyst is 1,400~3,000 %, wherein the synthetic yield of catalyst (%) is calculated by following equation, [the amount of synthesized carbon nanotube / the amount of input catalyst X 100].

Further, said step 1) comprises i) dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water to prepare the catalytic metal solution; ii) spraying said catalytic metal solution from the nozzle by gas atomization method using the 2~5 atm pressure of air; and iii) pyrolysis of sprayed solution in a reactor at 600~1,200℃ to obtain a catalyst composition wherein the apparent density of obtained catalyst composition is 0.03~0.4 g/cc.

Further, said metal precursor or inactive support precursor is in the form of nitrate, sulfate, alkoxide, chloride and/or carbonate of metal.

Further, the pressure of spray gas is 2.5~4.0 atm, and the temperature of pyrolysis is 600~1,000℃.

Further, said step 2) comprises i) pre-heating the reaction chamber; ii) fluidizing the catalyst composition in the reaction chamber after supplying the catalyst composition at the bottom of reaction chamber; iii) supplying the source gas comprising reaction gas and carrier gas at the bottom of reaction chamber; iv) thermal vapor deposition of the carbon on the fluidized metal catalyst by rotating impeller in the reaction chamber at 600~900℃; v) discharging the exhaust gas; and vi) selecting and obtaining a multi-walled carbon nanotube.

Further, said reaction gas is at least one selected from C1 to C4 saturated or unsaturated hydrocarbon, carbon monoxide or benzene, and said carrier gas is at least one selected from helium, nitrogen or argon.

Further, a catalyst composition for manufacturing multi-walled carbon nanotube can be represented by following formula:

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.3≤p≤3.0, 0.1≤q≤3.5, 0.05≤r≤1.0, 2.0≤s≤8.5.

Further, the catalyst composition for manufacturing multi-walled carbon nanotube can be represented by following formula:

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.5≤p≤2.5, 0.2≤q≤3.0, 0.1≤r≤0.8, 2.5≤s≤7.5.

Another object of the present invention is to provide a multi-walled carbon nanotube manufactured by said continuous process, wherein said multi-walled carbon nanotube has 5~15nm of fibrous diameter, 0.5~4㎛ of bundle diameter and 0.02~0.1 g/cc of apparent density.

The other object of the present invention is to provide a carbon nanotube-resin nano composite comprising the nano composite of multi-walled carbon nanotube of present invention and polymer resin, which shows excellent electrical conductivity, thermal conductivity, antistatic, electromagnetic waves shielding and/or mechanical properties.

The advantageous effect of present invention is to provide a catalyst and a continuous process for mass production of multi-walled carbon nanotube, which comprises i) preparing the catalyst composition comprising main catalyst (Fe, Co), co-catalyst (Mo) and inactive support (Al) for manufacturing the multi-walled carbon nanotube by spray pyrolysis method, ii) manufacturing the multi-walled carbon nanotube by thermal chemical vapor deposition method in a fluidized bed reactor, and iii) collecting and obtaining the manufactured multi-walled carbon nanotube, wherein the fibrous diameter is 5~15nm, the apparent density is 0.02~0.1 g/cc and the synthetic yield (%) of catalyst is 1,400~3,000 %.

Figure 1 illustrates one embodiment of an apparatus for preparing a catalyst composition for manufacturing multi-walled carbon nanotube by spray pyrolysis method of the present invention.

Figure 2 illustrates one embodiment of an apparatus for manufacturing multi-walled carbon nanotube by thermal chemical vapor deposition method of the present invention.

Figure 3 illustrates a flow chart for preparing a catalyst composition for manufacturing multi-walled carbon nanotube by spray pyrolysis method of the present invention.

Figure 4 illustrates a flow chart for manufacturing multi-walled carbon nanotube by thermal chemical vapor deposition method of the present invention.

The present invention relates to a continuous process for mass production of multi-walled carbon nanotube comprising: 1) obtaining a catalyst composition for manufacturing multi-walled carbon nanotube according to spray pyrolysis method after dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water; 2) synthesizing the multi-walled carbon nanotube by thermal chemical vapor deposition of the carbon on the metal catalyst at 600~900℃ with supplying source gas and catalyst composition in a fluidized bed reactor; and 3) selecting and obtaining a multi-walled carbon nanotube manufactured in step 2), wherein said catalyst composition comprises the main catalyst (Fe, Co), the co-catalyst (Mo) and the inactive support (Al); and the synthetic yield (%) of catalyst is 1,400~3,000 %, wherein the synthetic yield of catalyst (%) is calculated by following equation, [the amount of synthesized carbon nanotube / the amount of input catalyst X 100].

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.3≤p≤3.0, 0.1≤q≤3.5, 0.05≤r≤1.0, 2.0≤s≤8.5.

On the other hand, the present invention is to provide a multi-walled carbon nanotube manufactured by said continuous process, wherein said multi-walled carbon nanotube has 5~15nm of fibrous diameter, 0.5~4㎛ of bundle diameter and 0.02~0.1 g/cc of apparent density.

Further, the present invention is to provide a carbon nanotube-resin nano composite comprising the nano composite of multi-walled carbon nanotube and polymer resin, which shows excellent electrical conductivity, thermal conductivity, antistatic, electromagnetic waves shielding and/or mechanical properties.

The present invention can be explained in detail as follows.

In the present invention, the catalyst composition for manufacturing multi-walled carbon nanotube can be prepared by spray pyrolysis method as following steps.

(Step 1) This step is to dissolve the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water to prepare the catalytic metal solution.

In this step, said metal precursor or inactive support precursor is desirous in the form of nitrate, sulfate, alkoxide, chloride and/or carbonate of metal.

Figure 1 illustrates one embodiment of an apparatus for preparing a catalyst composition for manufacturing multi-walled carbon nanotube by spray pyrolysis method of the present invention. The catalytic metal solution has been prepared by dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water.

(Step 2) This step is to spray said catalytic metal solution from the nozzle by gas atomization method using the 2~5 atm pressure of air.

In this step, the catalytic metal solution has been supplied to the catalyst solution supply unit (140), while the spray gas, which is air, has been supplied to the gas supply unit (150) in the pressure of 2~5 atm. Then, the catalyst metal solution with 2~5 atm of air has been sprayed from the nozzle (130) to the reactor (110) by gas atomization method. At this time, ambient air has been input to the reactor and dispensed by air dispenser (170).

The pressure of spray gas is desirous in the range of 2.5~4.0 atm.

(Step 3) This step is to pyrolyze the sprayed solution in a reactor at 600~1,200℃ to obtain a catalyst composition wherein the apparent density of obtained catalyst composition is 0.03~0.4 g/cc.

The temperature of pyrolysis is desirous in the range of 600~1,000℃.

Further, the apparent density of obtained catalyst composition has to be in the range of 0.03~0.4 g/cc. If the apparent density is less than 0.03 g/cc, the catalytic yield is not enough because the amount of catalyst is lower than required amount. On the other hand, if the apparent density is more than 0.4 g/cc, the catalytic powder cannot be properly dispersed, which may cause the agglomeration and/or degradation of catalyst. Therefore, the catalytic yield is also declined.

On the other hand, the multi-walled carbon nanotube has been manufactured in the fluidized bed reactor according to the thermal chemical vapor deposition method with following steps.

(Step 1) This step is to pre-heat the reaction chamber. The reaction chamber (210) is a reaction space for synthesizing carbon nanotube, which is made by quartz or graphite.

(Step 2) This step is to fluidize the catalyst composition in the reaction chamber after supplying the catalyst composition at the bottom of reaction chamber. The catalyst composition is provided from dispersion hole in the catalyst supply part (220) and it is fluidized and dispersed in the reaction chamber.

(Step 3) This step is to supply the source gas comprising reaction gas and carrier gas at the bottom of reaction chamber. The source gas supplied from source gas supply part (230) comprises the reaction gas and the carrier gas. Further, the reaction gas is at least one selected from C1 to C4 saturated or unsaturated hydrocarbon, carbon monoxide or benzene, and the carrier gas is at least one selected from helium, nitrogen or argon.

(Step 4) This step is thermal chemical vapor deposition of the carbon on the fluidized metal catalyst by rotating impeller in the reaction chamber at 600~900℃. The reaction gas comprising C1 to C4 saturated or unsaturated hydrocarbon, carbon monoxide or benzene has been thermally deposited on the fluidized metal catalyst.

(Step 5) This step is to discharge the exhaust gas. The remaining gas and catalyst has to be discharged from the reactor as the exhaust gas. Therefore, the exhaust gas is discharged outside of reaction chamber through the exhaust gas discharge part (260).

(Step 6) The step is to select and to obtain a multi-walled carbon nanotube. The obtained multi-walled carbon nanotube has 5~15nm of fibrous diameter, 0.5~4㎛ of bundle diameter and 0.02~0.1 g/cc of apparent density.

On the other hand, the catalyst composition for manufacturing the multi-walled carbon nanotube can be explained in detail as follows.

As a main catalytic metal for producing carbon nanotube, iron (Fe), cobalt (Co) and/or nickel (Ni) has been already known. Further, chromium (Cr), manganese (Mn), molybdenum (Mo), vanadium (V), tungsten (W), tin (Sn), palladium (Pd) and/or copper (Cu) has been also known as a co-catalytic metal for producing carbon nanotube.

Further, an inactive support can be introduced in the catalyst composition for enhancing the catalytic activity.

Further, the essential component of catalyst composition for preparing multi-walled carbon nanotube can be predicted as follows. In the U.S. Pat. No. 8,048,821, Fe and Al have been regarded as essential component. In the U.S. Pat. No. 8,673,807, Co and Al have been regarded as essential component. In the U.S. Pat. No. 9,186,656, Fe and Mo have been regarded as essential component.

On the basis of inferred catalyst composition comprising main catalyst (Fe, Co), co-catalyst (Mo) and inactive support (Al), the inventors of present application have developed a catalyst and a continuous process for mass production of multi-walled carbon nanotube.

Further, the catalyst composition for manufacturing carbon nanotube in the present invention can be represented by the following formula.

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.3≤p≤3.0, 0.1≤q≤3.5, 0.05≤r≤1.0, 2.0≤s≤8.5.

Further, the preferred catalyst composition for manufacturing carbon nanotube in the present invention can be represented by the following formula.

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.5≤p≤2.5, 0.2≤q≤3.0, 0.1≤r≤0.8, 2.5≤s≤7.5.

Further, the multi-walled carbon nanotube according to present invention has 5~15nm of fibrous diameter, 0.5~4㎛ of bundle diameter and 0.02~0.1 g/cc of apparent density.

Further, a carbon nanotube-resin nano composite comprising the nano composite of multi-walled carbon nanotube manufactured according to continuous process for mass production and polymer resin shall show excellent electrical conductivity, thermal conductivity, antistatic, electromagnetic waves shielding and/or mechanical properties.

Therefore, it has been expected that carbon nanotube will be applied to aerospace material, biotechnology, environmental energy material, medicine and therapeutics and/or electronic computer in the near future.

The present invention can be explained more concretely by following Examples and Comparative Examples. However, the scope of the present invention cannot be limited by following Examples.

Examples

(Preparation Example 1) Preparation of catalyst composition for manufacturing carbon nanotube of the present invention

Catalyst 1 (Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5)

For preparing catalytic metal solution, 2.0 mole of Fe(NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Then, the catalytic metal solution has been sprayed into the reactor from the nozzle at 0.3L/hour feeding rate using air as carrier gas. The pyrolysis of catalytic metal has been made inside of the reactor. The conditions of pyrolysis can be as follows, 3 atm of air, 750℃ of the temperature of inside reactor and 120 minutes of operation time. Finally, 57g of catalyst composition has been obtained. The molar ratio of metal components can be Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5 and the apparent density of catalyst composition can be 0.28g/ml.

(Preparation Example 2) Preparation of catalyst composition for manufacturing carbon nanotube of the present invention

Catalyst 2 (Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5)

For preparing catalytic metal solution, 2.0 mole of Fe (NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Then, the catalytic metal solution has been sprayed into the reactor from the nozzle at 0.3L/hour feeding rate using air as carrier gas. The pyrolysis of catalytic metal has been made inside of the reactor. The conditions of pyrolysis can be as follows, 3 atm of air, 850℃ of the temperature of inside reactor and 120 minutes of operation time. Finally, 53g of catalyst composition has been obtained. The molar ratio of metal components can be Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5 and the apparent density of catalyst composition can be 0.25g/ml.

(Comparative Preparation Example 1) Preparation of catalyst composition for manufacturing carbon nanotube (Difference of molar fraction ratio)

Catalyst C-1 (Fe/Co/Mo/Al = 0.1/3.9/0.5/5.5)

For preparing catalytic metal solution, 0.1 mole of Fe (NO₃)₃·9H₂O, 3.9 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Then, the catalytic metal solution has been sprayed into the reactor from the nozzle at 0.3L/hour feeding rate using air as carrier gas. The pyrolysis of catalytic metal has been made inside of the reactor. The conditions of pyrolysis can be as follows, 3 atm of air, 750℃ of the temperature of inside reactor and 120 minutes of operation time. Finally, 52g of catalyst composition has been obtained. The molar ratio of metal components can be Fe/Co/Mo/Al = 0.1/3.9/0.5/5.5 and the apparent density of catalyst composition can be 0.38g/ml.

(Comparative Preparation Example 2) Preparation of catalyst composition for manufacturing carbon nanotube (Difference of catalyst pyrolysis temperature)

Catalyst C-2 (Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5)

For preparing catalytic metal solution, 2.0 mole of Fe (NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Then, the catalytic metal solution has been sprayed into the reactor from the nozzle at 0.3L/hour feeding rate using air as carrier gas. The pyrolysis of catalytic metal has been made inside of the reactor. The conditions of pyrolysis can be as follows, 3 atm of air, 400℃ of the temperature of inside reactor and 120 minutes of operation time. Finally, 66g of catalyst composition has been obtained. The molar ratio of metal components can be Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5 and the apparent density of catalyst composition can be 0.41g/ml.

(Comparative Preparation Example 3) Preparation of catalyst composition for manufacturing carbon nanotube (Co-precipitation method)

Catalyst C-3 (Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5)

For preparing Solution A, 2.0 mole of Fe (NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 0.5L of deionized water at room temperature by stirring for 2 hours. For preparing Solution B, 4 mole of NH₄·HCO₃ have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Solution A and Solution B have been mixed and stirred at room temperature for 60 minutes. After filtering the obtained solid material, the filtered cake has been collected after washing it with deionized water. The collected filtered cake has been dried in 120℃ of air for 12 hours. After crashing the filtered cake, crashed cake has been calcinated at 600℃ for 4 hours in air circumstance. Finally, 81g of catalyst composition has been obtained, after crashing the calcinated powder one more time. The molar ratio of metal components can be Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5 and the apparent density of catalyst composition can be 0.78g/ml.

(Comparative Preparation Example 4) Preparation of catalyst composition for manufacturing carbon nanotube (Spray-drying method)

Catalyst C-4 (Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5)

For preparing Solution A, 2.0 mole of Fe (NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O, 0.5 mole of (NH₄)₆Mo₇O₂₄·4H₂O and 5.5 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 0.5L of deionized water at room temperature by stirring for 2 hours. For preparing Solution B, 4 mole of NH₄·HCO₃ have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Solution A and Solution B have been mixed and stirred at room temperature for 60 minutes. After filtering the obtained solid material, the filtered cake has been collected after washing it with deionized water. The collected filtered cake has been added and stirred in 1L of deionized water for preparing catalytic metal solution. After spray-drying the obtained catalytic metal solution at 230℃, dried catalyst powder has been collected. Finally, 95g of catalyst composition has been obtained after calcinating the dried catalyst powder at 600℃ of air for 4 hours. The molar ratio of metal components can be Fe/Co/Mo/Al = 2.0/2.0/0.5/5.5 and the apparent density of catalyst composition can be 0.92g/ml.

(Comparative Preparation Example 5) Preparation of catalyst composition for manufacturing carbon nanotube (Without Mo)

Catalyst C-5 (Fe/Co/Al = 2.0/2.0/6.0)

For preparing catalytic metal solution, 2.0 mole of Fe (NO₃)₃·9H₂O, 2.0 mole of Co(NO₃)₂·6H₂O and 6.0 mole of Al(NO₃)₃·9H₂O have been added and dissolved in 1L of deionized water at room temperature by stirring for 2 hours. Then, the catalytic metal solution has been sprayed into the reactor from the nozzle at 0.3L/hour feeding rate using air as carrier gas. The pyrolysis of catalytic metal has been made inside of the reactor. The conditions of pyrolysis can be as follows, 3 atm of air, 750℃ of the temperature of inside reactor and 120 minutes of operation time. Finally, 67g of catalyst composition has been obtained. The molar ratio of metal components can be Fe/Co/Al = 2.0/2.0/6.0 and the apparent density of catalyst composition can be 0.40g/ml.

(Example 1) Synthesis of carbon nanotube

The catalysts prepared in Preparation Examples 1 and 2 (catalyst 1, catalyst 2) and Comparative Preparation Examples 1-5 (Catalyst C-1, C-2, C-3, C-4 and C- 5) have been adopted for preparing carbon nanotube in the fluidized bed reactor as shown in Fig. 2. The carbon nanotube has been manufactured at 600~900℃ on the catalyst powder by thermal chemical vapor deposition method after supplying and dispersing the catalyst powder as well as supplying and injecting the source gas in the fluidized bed reactor. The mixed gas of ethylene as a reaction gas and nitrogen gas as a carrier gas in the volume ratio 3:1 has been used as source gas. Table 1 shows the synthetic yield of catalyst (%) and the apparent density of multi-walled carbon nanotube.

The synthetic yield of catalyst (%) can be calculated by following equation,

[The synthetic yield of catalyst (%) = the amount of synthesized carbon nanotube / the amount of input catalyst X 100].

[The amount of synthesized carbon nanotube = the total amount of reaction product (M_total) - the amount of input catalyst (M_cat)]

Table 1

	The amount of input catalyst (g)	Reaction temp. (℃)	Volume of reaction gas (mL/min.)	Reaction time (hour)	Synthetic yield of catalyst (%)	Apparent density (g/cc)
Catalyst 1	100	750	C₂H₄:N₂=30:10	1.5	2,420	0.04
Catalyst 2					2,740	0.035
Catallyst C-1					1,650	0.06
Catalyst C-2					1,390	0.09
Catalyst C-3					920	0.13
Catalyst C-4					1,140	0.12
Catalyst C-5					680	0.15

The synthetic yield of catalyst [Fep, Coq, Mor, Als] has been measured after obtaining the multi-walled carbon nanotube according to the continuous process of present invention. The synthetic yield of Catalyst 1 and Catalyst 2 showed 2,420% and 2,740% respectively. However, if the composition of catalyst metal has been changed, the synthetic yield of catalyst has been declined into only 1,650% (Catalyst C-1, changing the molar fraction ratio of catalyst metal) and 680% (Catalyst C-5, Mo excluded). Further, the synthetic yield of Catalyst C-2 also has been declined into 1,390% because of low pyrolysis temperature. Of course, the synthetic yield of Catalyst C-3 (prepared by co-precipitation method) and Catalyst C-4 (prepared by spray-drying method) also have been declined into 920% and 1,140% respectively.

Therefore, in case of catalyst composition of present invention [Fep, Coq, Mor, Als], the multi-walled carbon nanotube can be manufactured in a high synthetic yield of catalyst between 1,400 and 3,000% according to the continuous manufacturing process of present invention.

Description of reference numeral

100: catalyst production apparatus

110: reactor for producing catalyst

120: heating unit

130: nozzle

140: catalyst solution supply unit

150: gas supply unit

160: air supply unit

170: air dispenser

200: fluidized bed reactor

210: reaction chamber

220: catalyst supply part

222: catalyst

224: catalyst supply pipe

230: source gas supply part

232: source gas

234: source gas supply pipe

240: rotating impeller

242: rotation motor

250: heating part

260: exhaust gas discharge part

Claims

A continuous process for mass production of multi-walled carbon nanotube comprising

1) obtaining a catalyst composition for manufacturing multi-walled carbon nanotube according to spray pyrolysis method after dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water;

2) synthesizing the multi-walled carbon nanotube by thermal chemical vapor deposition of the carbon on the metal catalyst at 600~900℃ with supplying source gas and catalyst composition in a fluidized bed reactor; and

3) selecting and obtaining a multi-walled carbon nanotube manufactured in step 2);

wherein said catalyst composition comprises the main catalyst (Fe, Co), the co-catalyst (Mo) and the inactive support (Al); and the synthetic yield (%) of catalyst is 1,400~3,000 %,

wherein the synthetic yield of catalyst (%) is calculated by following equation,

[the amount of synthesized carbon nanotube / the amount of input catalyst X 100].
The continuous process for mass production of multi-walled carbon nanotube according to claim 1,

wherein said step 1) comprises

i) dissolving the catalyst metal precursor (Fe, Co, Mo) and the inactive support precursor (Al) in the de-ionized water to prepare the catalytic metal solution;

ii) spraying said catalytic metal solution from the nozzle by gas atomization method using the 2~5 atm pressure of air; and

iii) pyrolysis of sprayed solution in a reactor at 600~1,200℃ to obtain a catalyst composition

wherein the apparent density of obtained catalyst composition is 0.03~0.4 g/cc.
The continuous process for mass production of multi-walled carbon nanotube according to claim 2, wherein said metal precursor or inactive support precursor is in the form of nitrate, sulfate, alkoxide, chloride and/or carbonate of metal.
The continuous process for mass production of multi-walled carbon nanotube according to claim 2, wherein the pressure of spray gas is 2.5~4.0 atm, and the temperature of pyrolysis is 600~1,000℃.
The continuous process for mass production of multi-walled carbon nanotube according to claim 1,

wherein said step 2) comprises

i) pre-heating the reaction chamber;

ii) fluidizing the catalyst composition in the reaction chamber after supplying the catalyst composition at the bottom of reaction chamber;

iii) supplying the source gas comprising reaction gas and carrier gas at the bottom of reaction chamber;

iv) thermal vapor deposition of the carbon on the fluidized metal catalyst by rotating impeller in the reaction chamber at 600~900℃;

v) discharging the exhaust gas; and

vi) selecting and obtaining a multi-walled carbon nanotube.
The continuous process for mass production of multi-walled carbon nanotube according to claim 5, wherein said reaction gas is at least one selected from C1 to C4 saturated or unsaturated hydrocarbon, carbon monoxide or benzene, and said carrier gas is at least one selected from helium, nitrogen or argon.
The continuous process for mass production of multi-walled carbon nanotube according to any claims of 1 to 6,

wherein a catalyst composition for manufacturing multi-walled carbon nanotube can be represented by following formula:

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.3≤p≤3.0, 0.1≤q≤3.5, 0.05≤r≤1.0, 2.0≤s≤8.5.
The continuous process for mass production of multi-walled carbon nanotube according to claim 7,

wherein the catalyst composition for manufacturing multi-walled carbon nanotube can be represented by following formula:

Fe_p, Co_q, Mo_r, Al_s

wherein

p, q, r, s represent the molar fraction of Fe, Co, Mo, Al respectively,

p + q + r + s = 10

0.5≤p≤2.5, 0.2≤q≤3.0, 0.1≤r≤0.8, 2.5≤s≤7.5.
A multi-walled carbon nanotube manufactured by the continuous process according to claim 1, wherein said multi-walled carbon nanotube has 5~15nm of fibrous diameter, 0.5~4㎛ of bundle diameter and 0.02~0.1 g/cc of apparent density.
A carbon nanotube-resin nano composite comprising the nano composite of multi-walled carbon nanotube manufactured according to continuous process for mass production of claim 1 and polymer resin, which shows excellent electrical conductivity, thermal conductivity, antistatic, electromagnetic waves shielding and/or mechanical properties.