Supported catalyst, carbon nanotube assembly, and preparation method therefor

Abstract

The present invention relates to an impregnated supported catalyst, a carbon nanotube aggregate, and a method for producing the carbon nanotube aggregate. The carbon nanotube aggregate includes a four-component catalyst in which catalytic components and active components are supported on a granular support, and bundle type carbon nanotubes grown on the catalyst. The carbon nanotube aggregate has an average particle diameter of 100 to 800 μm, a bulk density of 80 to 250 kg/m 3 , and a spherical or potato-like shape.

1 . An impregnated supported catalyst prepared by sequentially adding a multi-carboxylic acid and precursors of first and second catalytic components to precursors of first and second active components to obtain a transparent aqueous metal solution, impregnating an aluminum-based granular support with the transparent aqueous metal solution, followed by drying and calcination, wherein the supported catalyst has a bulk density of 0.8 to 1.5 g/cm 3 . 
     
     
         2 . The impregnated supported catalyst according to  claim 1 , wherein the catalyst comprises first and second catalytic components and first and second active components, and the number of moles (x) of the first catalytic component, the number of moles (y) of the second catalytic component, the number of moles (p) of the first active component, and the number of moles (q) of the second active component with respect to 100 moles of the support satisfy the following relationships:
   10≦ x≦ 40;
     1≦ y≦ 20;
     0.1≦ y/[x+y]≦ 0.5;
     1≦ p+q≦ 20; and
     0.1≦[ p+q]/[x+y]≦ 0.5.
   
     
     
         3 . The impregnated supported catalyst according to  claim 1 , wherein the granular support has a bulk density of 0.6 to 1.2 g/cm 3 , and the catalyst in which the catalytic components and the active components are supported has a bulk density of 0.8 to 1.5 g/cm 3 . 
     
     
         4 . The impregnated supported catalyst according to  claim 1 , wherein the granular support has an aspect ratio of 1.2 or less, and the average aspect ratio (As) of the support before the catalytic components and the active components are supported on the support and the average aspect ratio (A CAT ) of the catalyst after the catalytic components and the active components are supported on the support satisfy 0.8≦A CAT /As≦1.2. 
     
     
         5 . The impregnated supported catalyst according to  claim 1 , wherein the multi-carboxylic acid is used in an amount of 0.2 to 2.0 moles, assuming that the sum of the moles (p+q) of the first and second active components equals to 1. 
     
     
         6 . The impregnated supported catalyst according to  claim 1 , wherein the multi-carboxylic acid is selected from dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids, and mixtures thereof. 
     
     
         7 . The impregnated supported catalyst according to  claim 1 , wherein the calcination is performed at 650 to 800° C. 
     
     
         8 . The impregnated supported catalyst according to  claim 1 , wherein the first catalytic component is cobalt (Co), the second catalytic component is selected from iron (Fe), nickel (Ni), and a mixture thereof, the first active component is molybdenum (Mo), and the second active component is vanadium (V). 
     
     
         9 . The impregnated supported catalyst according to  claim 1 , wherein the first and second active components are in a weight ratio of 6-0.1:0.1-6. 
     
     
         10 . The impregnated supported catalyst according to  claim 1 , wherein the catalyst has a structure in which the surface and pores of the aluminum-based support are coated with a monolayer or multilayer of the catalytic components and the active components, and the amount of a fine powder having a number average particle diameter not larger than 32 μm, as measured after ultrasonic shaking at 40 watts for 1 minute, is 10% or less of the amount of the catalyst. 
     
     
         11 . The impregnated supported catalyst according to  claim 6 , wherein the transparent aqueous metal solution has a concentration of 0.01 to 0.4 g/ml. 
     
     
         12 . A carbon nanotube aggregate comprising the impregnated supported catalyst according to  claim 1  and bundle type carbon nanotubes grown on the catalyst wherein the carbon nanotube aggregate has an average particle diameter of 100 to 800 μm, a bulk density of 80 to 250 kg/m 3 , and a spherical or potato-like shape. 
     
     
         13 . The carbon nanotube aggregate according to  claim 12 , wherein the carbon nanotubes have an aspect ratio of 0.9 to 1 and a strand diameter of 10 to 50 nm. 
     
     
         14 . The carbon nanotube aggregate according to  claim 12 , wherein the catalyst has an average aspect ratio (A CAT ) of 1.2 or less and the carbon nanotube aggregate has an average aspect ratio (A CNT ) of 1.2 or less. 
     
     
         15 . The carbon nanotube aggregate according to  claim 12 , wherein the bundle type carbon nanotubes have a particle size distribution (Dcnt) of 0.5 to 1.0. 
     
     
         16 . A method for producing a carbon nanotube aggregate, comprising:
 1) sequentially blending a multi-carboxylic acid component and an aqueous solution of precursors of first and second catalytic components with an aqueous solution of precursors of first and second active components to obtain a transparent aqueous metal solution, and mixing an aluminum-based granular support with the transparent aqueous metal solution;   2) drying the mixture under vacuum at 40 to 80° C. and calcining the dried mixture at 650 to 800° C. to obtain a catalyst for carbon nanotube production in which the surface and pores of the aluminum-based support are impregnated and coated with the catalytic components and the active components;   3) feeding the catalyst for carbon nanotube production into a fluidized bed reactor and introducing at least one carbon source selected from C 1 -C 4  saturated or unsaturated hydrocarbons, and optionally together with a mixed gas hydrogen and nitrogen, into the reactor at 500 to 900° C.; and   4) decomposing the carbon source and growing carbon nanotubes on the catalyst surface by chemical vapor synthesis.   
     
     
         17 . The method according to  claim 16 , further comprising aging at 45 to 80° C. before the drying under vacuum in step 2). 
     
     
         18 . The method according to  claim 16 , further comprising preliminarily calcining at 250 to 400° C. before the calcination in step 2). 
     
     
         19 . The method according to  claim 18 , further comprising impregnating a portion of the total amount of the aqueous metal solution into the aluminum-based granular support just before the preliminary calcination and impregnating the remainder of the aqueous metal solution into the aluminum-based granular support just before the calcination.