Process for purifying carbon nanotubes made on refractory oxide supports
View Patent ↗A carbon nanotube material that comprises carbon nanotubes, a magnesia support and a catalyst metal can be purified by contacting it with a mixture comprising carbon dioxide and water. At least some of the magnesia support is reacted to form water-soluble compounds.
1. A method for purifying carbon nanotube material comprising, contacting a carbon nanotube material comprising carbon nanotubes, a magnesia support and a catalyst transition metal with a mixture comprising carbon dioxide and water, wherein the liquid mixture comprising carbon dioxide and water reacts with at least some of the magnesia support to form water-soluble compounds, and wherein the liquid mixture comprising carbon dioxide and water reacts with at least some of the catalyst transition metal to form water-soluble compounds.
2. The method of claim 1 further comprising separating the water-soluble compounds from the carbon nanotubes.
3. The method of claim 1 wherein the mixture further comprises a complexing agent.
4. The method of claim 1 wherein the contacting step is done more than once.
5. The method of claim 1 wherein the contacting step is done at a temperature between about 0° C. and about 40° C.
6. The method of claim 1 wherein the contacting step is done at a temperature between about 0° C. and about 30° C.
7. The method of claim 1 wherein the contacting step is done at a temperature between about 0° C. and about 20° C.
8. The method of claim 1 further comprising treating the carbon nanotube material with an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and combinations thereof.
9. The method of claim 1 wherein the mixture further comprises a water-soluble amine.
10. The method of claim 1 wherein the mixture further comprises a chelating agent.
11. The method of claim 1 wherein mixture further comprises a reducing agent.
12. The method of claim 1 wherein the mixture further comprises sodium hydrosulfite, sodium bisulfite or both.
13. The method of claim 1 wherein the contacting is done in a continuous flow of the mixture comprising carbon dioxide and water.
14. The method of claim 1 further comprising heating the carbon nanotube material in an oxidative environment at a temperature in a range of about 100° C. and about 400° C.
15. The method of claim 1 where the contacting step is done more than once and wherein a reducing agent is added to the mixture after a first contacting.
16. The method of claim 1 where the contacting step is done more than once and after a first contacting, the mixture further comprises a reducing agent.
17. The method of claim 1 where the contacting step is done more than once and after a first contacting, the mixture further comprises a chelating agent.
18. The method of claim 1 where the contacting step is done more than once and after a first contacting, the mixture further comprises a complexing agent.
19. The method of claim 1 where the contacting step is done more than once and after a first contacting, the mixture further comprises a water-soluble amine.
20. The method of claim 1 where the contacting step is done more than once and after a first contacting, the mixture further comprises sodium hydrosulfite, sodium bisulfite or both.