II International Symposium on Carbon for Catalysis ABSTRACTS

OP-I-2
loading. It is also interesting to observe that the particle sizes only increase very slightly with
the metal loading.
TEM characterization demonstrates that all the cobalt is deposited on the fibres, free of
any bulk precipitation. A representative TEM image of the 40 wt.% Co/CNF catalyst is shown
in Fig. 1. The cobalt oxide particles are homogeneously distributed with a very narrow size
distribution, and seem to cover the fibre uniformly at the 40 wt.% loading. The average
particle size calculated from 120 particles is 8.3 nm, in good agreement with the XRD study.
TPR study shows that all the catalysts are reduced through two main steps, from Co 3 O 4 to
CoO, and from CoO to Co. The first peak is relatively narrow and the second peak is quite
broad. This also suggests the coexistence of Co 3 O 4 and CoO. Compared with the reduction of
Co/Al 2 O 3 , Co/CNF is reduced at a lower temperature. This is because for Co/Al 2 O 3 , cobalt
will form a surface compound with alumina, which is difficult to be reduced. Hence, TPR
study clearly shows the weak interaction of metal and CNF. This will also be an advantage of
using CNF as support for F-T catalysts because high reduction temperatures are required for
cobalt on strongly interaction supports, and they lead to the sintering of cobalt particles.
In conclusion, DP has been used to prepare highly loaded, highly dispersed cobalt on
CNF catalysts. The precipitation has been controlled by slowly increase the pH of the
solution. The Co/CNF catalysts have a small particle size and narrow particle size
distribution. Combined with their easy-to-reduce property, these catalysts could be promising
for F-T synthesis applications.
Table 1. Metal loading and particle sizes from catalyst. Fig. 1. TEM image of the 40 wt.%
XRD and TEM of different catalysts.
Catalyst Actual loading Particle size Particle size
(wt.%) (nm, XRD) (nm, TEM)
12 wt.% 10.1 8.4 6.5
20 wt.% 17.1 9.5 -
40 wt.% 38.6 9.4 8.3
References:
1 G.L. Bezemer, A. van Laak, A.J. van Dillen and K.P. de Jong, Stud. Surf. Sci. Catal. 147
(2004) 259.
2 J.H. Bitter, M.K. van der Lee, A.G.T. Slotboom, A.J. van Dillen, and K.P. de Jong, Catal.
Lett. 89 (2003) 139.
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