II International Symposium on Carbon for Catalysis ABSTRACTS

TOWARDS LARGE SCALE PRODUCTION OF CNF FOR CATALYTIC
APPLICATIONS
OP-<strong>II</strong>-3
Kvande I., Yu Z., Rønning M., Holmen A., Chen D.
Department of Chemical Engineering, Norwegian University of Science and Technology,
NTNU, N-7491 Trondheim, Norway
e-mail: kvandei@chemeng.ntnu.no
Carbon nanofibres (CNF) have recently gained much interest for a series of applications due
to their unique properties [1]. In particular, the inertness, the presence of stabilizing surface
groups, and the conductivity and mesoporous character are thought to be interesting in terms
of heterogeneous catalysis and electrocatalysis. The commercialization and use of CNFs relies
on improving the synthesis process aiming at reducing the production costs and controlling
the quality. Two main issues for the CNF production by catalytic chemical vapor deposition
are addressed in this work. One is the effect of the residence time on CNF productivity and
carbon structure relating to scale up of CNF-production and the other one is to directly use
CNF to replace ceramics as supports for CNF-synthesis, in order to significantly reduce the
requirement of CNF purification [2]. This possibility is being tested by synthesizing CNF
from Ni/CNF catalysts. The challenges are addressed and some ideas for overcoming the
obstacles are proposed.
The Tapered Element Oscillating Microbalance (TEOM) has been shown to be a
powerful tool to study the kinetics of CNF synthesis, and was used to identify the most
important parameters for scaling up Fishbone-CNF production. The effect of temperature and
partial pressure of H 2 on CNF growth were studied on a hydrotalcite derived Ni catalyst. The
results indicate that the optimal temperature is around 580 ºC, and that hydrogen partial
pressure has a significant effect on the growth rate, as shown in Fig. 1. There exists an
optimum partial pressure for CNF production, and the growth rate is significantly lower at
higher partial pressures of hydrogen. The results suggest that the residence time of methane in
the reactor will have a significant effect on the growth rate, since hydrogen is the product of
methane decomposition. A series of large scale experiments has been performed in a fixed
bed reactor with a production capacity of about 1kg of CNF per batch, as a benchmark for
process scaling. Synthesis was performed in a ceramic reactor at 580 ºC with space velocities
of methane ranging from 4.6 to 410 l/gcat h, corresponding to different conversions and thus
different partial pressures of hydrogen. Fig. 2 clearly shows a higher coking rate at higher
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