II International Symposium on Carbon for Catalysis ABSTRACTS

OP-<strong>II</strong>-5
3. Results and discussion
A novel type of honeycomb monolith has been synthesised coated with an even layer of
mesoporous carbon nanofibres (CNFs) with relatively small diameter as shown in figure 1.
The CNF layer completely covers the surface of the monolith walls with a uniform thickness.
a
b
50 μm
2 μm
Figure1. SEM images of CNF layer grown with ethane:H 2 mixture at 873 K. a) corner detail, b) layer detail
It was found that the thickness of the CNF layer and the growth rate of the fibres have
significant effects on the properties of the CNF-monolith composite. The preferred conditions
are a mixture of C 2 H 6 : H 2 as the carbon source and temperatures around 873-923 K. The
CNF layer exhibits a relatively strong adhesion as tested by ultrasonic treatment. The porosity
in the composite lies in the mesoporous range centered at approximately 17 nm pore size.
This fact together with the absence of microporosity is advantageous for the diffusion of
reactants in liquid phase reactions and improves the properties of previously reported
CNF-monolith composites [6].
The CNF layer thickness and the CNF diameter can be tuned by the reaction temperature. For
the same growing times, temperatures of 873 K and 923 K resulted in CNF layer thickness of
2 and 4 μm, respectively. CNFs with diameters of 5-10 nm with a narrow distribution are
attained at 873 K. Larger diameters (10-30 nm) are found at 923 K and higher temperatures.
The thin alumina coating (0.1 μm) prevents CNFs to be trapped inside the alumina and most
of the CNFs are present as a uniform coating at the outermost surface of the monolith walls.
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