Page 28 - Carbon Nanotubes

Catalytic production and purification of nanotubules 19

Fig. 4. Catalytic particles encapsulated in tubules on Co-SO,: (a) low magnification; (b) HREM.

Fig. 5. Acetylene decomposition on Co-HY (973 K, 30 minutes): (a) encapsulated metal particle; (b) carbon
filaments (A) and tubules of small diameters (B) on the surface of the catalyst.

silica catalyst synthesized by the ion-exchange- relatively. The optimal C,H, rate was found to be
precipitation method. This method leads to a better 0.34 mol g-' h-'. At this rate, 40-50 wt% of carbon
dispersion and a sharper size distribution than porous precipitates on the catalyst surface after 30 minutes
impregnation (Fig. 6). The rate of acetylene was of reaction. The increase of acetylene rate leads to an
varied from 0.15 to 0.59 mol C,H, g-' h-'. The increase of the -amount of amorphous carbon (equal
amount of condensed carbon at 973 K changed as a to 2 wt% on the external walls of the tubules, for
function of hydrocarbon rate from 20 to 50 wt% optimal conditions).