Single-walled carbon nanotube catalysts and method for preparing same
View Patent ↗An activated catalyst capable of selectively growing single-walled carbon nanotubes when reacted with carbonaceous gas is provided. The activated catalyst is formed by reducing a catalyst that comprises a complex oxide. The complex oxide may be of formula A x-w F w B y-v G v O z wherein x/y≦2; z/y≦4; 0≦w≦0.3x; 0≦v≦0.3y; A is a Group VIII element; F is an element that is different from A but has, in said composition, the same valence state as A; B is an element different from A and F, and is an element whose simple oxide, in which B is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.; G is an element different from A, B and F, and is an element whose simple oxide, in which G is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.; and O is oxygen. The complex oxide is reduced at a temperature less that 950° C. Methods of making, uses for and carbon fibril-containing product made with these activated catalysts are also provided.
1. A method of making single walled carbon nanotubes comprising:
providing a composition comprising a complex oxide having a formula
A x-w F w B y-v G v O z
wherein
x/y≦2;
z/y ≦4;
0≦w≦0.3x;
0≦v≦0.3y;
A is a Group VIII element;
F is an element that is different from A but has, in said composition, the same valence state as A;
B is an element different from A and F, and is an element whose simple oxide, in which B is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.;
G is an element different from A, B and F, and is an element whose simple oxide, in which G is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.;
O is oxygen;
reducing said composition to form an activated catalyst;
contacting a carbonaceous gas with said activated catalyst under suitable conditions for growing single walled carbon nanotubes, said suitable conditions including pressure greater than about 1 atmosphere and less than about 10 atmospheres and temperature greater than about 400° C. and less than about 950° C.; and
growing carbon nanotubes on said activated catalyst, said carbon nanotubes comprising single walled carbon nanotubes.
2. The method of claim 1 , wherein said A is iron, nickel or cobalt.
3. The method of claim 1 , wherein said B is aluminum, lanthanum, magnesium, silicon, titanium, zinc, zirconium, yttrium, calcium, strontium, molybdenum or barium.
4. The method of claim 1 , wherein said carbon nanotubes comprise at least 50% single walled carbon nanotubes.
5. The method of claim 1 , wherein said B is magnesium and G is calcium or strontium.
6. The method of claim 5 , wherein said A is cobalt and F is iron, aluminum, lanthanum, manganese, chromium, copper or yttrium.
7. The method of claim 1 wherein said A is cobalt, F is molybdenum, B is magnesium and G is calcium or strontium.
8. The method of claim 1 , wherein said reducing step and said contacting step occur contemporaneously.
9. A method of making single walled carbon nanotubes comprising:
contacting a carbonaceous gas with an activated catalyst in a reaction zone at suitable conditions for growing single walled carbon nanotubes, said suitable conditions including a pressure greater than about 1 atmosphere and less than about 10 atmospheres and temperature greater than about 400° C. and less than about 950° C.,
said activated catalyst comprising a reduced form of a complex oxide, said complex oxide having a formula
A x-w F w B y-v G v O z
wherein
x/y ≦2;
z/y ≦4;
0≦w≦0.3x;
0≦v≦0.3y;
A is a Group VIII element;
F is an element that is different from A but has, in said composition, the same valence state as A;
B is an element different from A and F, and is an element whose simple oxide, in which B is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.;
G is an element different from A, B and F, and is an element whose simple oxide, in which G is at the same valence state as in the complex oxide, is not reducible in the presence of hydrogen gas at a temperature less than about 900° C.;
O is oxygen; and
growing carbon nanotubes on said activated catalyst, said carbon nanotubes comprising single walled carbon nanotubes.
10. The method of claim 9 , wherein said A is iron, nickel or cobalt.
11. The method of claim 9 , wherein the B is aluminum, lanthanum, magnesium, silicon, titanium, zinc, zirconium, yttrium, calcium, strontium, molybdenum or barium.
12. The method of claim 9 , wherein said carbon nanotubes comprise at least 50% single walled carbon nanotubes.
13. The method of claim 9 , wherein said B is magnesium and G is calcium or strontium.
14. The method of claim 13 , wherein said A is cobalt and F is iron, aluminum, lanthanum, manganese, chromium, copper or yttrium.
15. The method of claim 9 , wherein said A is cobalt, F is molybdenum, B is magnesium and G is calcium or strontium.
16. The method of claim 1 , further comprising adding a reduction catalyst to said composition prior to the reducing step,
wherein said reduction catalyst is a Group VIII, Group VI or Group I metal or its simple metal oxide,
and wherein said reduction catalyst is not part of said complex oxide.
17. The method of claim 16 , wherein said reduction catalyst is Pd or Pt.
18. The method of claim 17 , wherein said reduction catalyst is 0.1-5% by weight of element A.
19. The method of claim 1 , wherein the catalyst comprises spinel.
20. The method of claim 9 , wherein the catalyst comprises spinel.
21. The method of claim 4 , wherein said method comprises a yield greater than 1.0 gm carbon/gm catalyst.
22. The method of claim 12 , wherein said method comprises a yield greater than 1.0 gm carbon/gm catalyst.