II International Symposium on Carbon for Catalysis ABSTRACTS

PP-<strong>II</strong>-26
open macrostructure with a porosity of 81%. Inconel 601 is an alloy of nickel, iron and
chromium as the main components. The CNF were produced by catalytic decomposition of
ethane on SMF Inconel in the presence of hydrogen in a ratio 15:85 at 1.25 bar. The reaction
temperature was varied between 630 and 680°C.
The SMF filters were first oxidized in air at 650°C during 3 hours. This treatment brings
a mechanic stress in the metal leading to the formation of cracks and bumps. This surface
deformation allows the increase of the surface area and, consequently, the amount of metal in
contact with the reactive gas. In order to reduce the oxides, the filters were the treated in
hydrogen for 2 hours at 600°C. SEM and XPS analysis of the filters were carried out to
investigate the state of the metallic surface of the filters.
The rate of carbon deposition on the filters was measured, showing a fast increase of
carbon mass on the sample during the first minutes. Afterwards, a 4 hours period of
increasing rate of carbon deposition followed by a deactivation phase was observed.
In order to control the growth of CNF, the kinetics of ethane decomposition on SMF Inconel
was studied. Partial orders of 1 and -2 for C 2 H 6 and H 2 respectively and an apparent activation
energy of 235 kJ/mol were found. These results are at variance with the widely accepted
hypothesis of carbon diffusion in the metal as the rate limiting step. SEM studies and the
kinetics results suggests a CNF growth mechanism on SMF Inconel with the C - C bond scission
as the rate determining step.
All kinetic results and the SEM characterization will be reported and the growth
mechanism with will be discussed.
References
1 K.P. De Jong and J.W. Geus, Catal. Rev.-Sci. Eng., 42 (4), 2000: p. 481-510.
2 P. Tribolet and L. Kiwi-Minsker, Catal. Today, 102-103, 2005: p. 15-22.
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