Towards Large Scale Production of CNF for Catalytic Applications
I. Kvande, Z. Yu, T. Zhao, M. RГёnning, A. Holmen and D. Chen
Department of Chemical Engineering, Norwegian University of Science and Technology, NTNU, N-7491 Trondheim (Norway)
E-mail: chen@chemeng.ntnu.no
Pages: 583-589
Abstract
A systematic investigation of carbon nanotubes (CNT) and nanofibre (CNF) growth in terms of structures of carbon nanomaterials and growth rates by chemical vapour deposition is summarized. Different catalysts such as unsupported Fe3O4 and supported Ni, Fe and NiFe catalysts and different carbon sources such as CO, CO/H2, CH4/H2, C2H6/H2 and C2H4/CO/H2 have been applied. This short review has been addressed to identify the principles for controlled synthesis of carbon nanotube or nanofibre with well-defined structures. The production of relatively high yields of defined structures is obtained. The Ni catalyst produces almost exclusively fishbone CNFs, while the supported Fe catalyst produces multiwall CNTs (MWCNTs). The NiFe catalyst can give a structure intermediate of the two. Unsupported Fe3O4 results in the platelet structure. The diameter of the produced structures holds information on the growth mechanism. The diameters of the MWNTs are always smaller than the growth catalyst particles, while the fishbone CNFs always have larger diameter than the growth catalyst. The structure and growth rate reflect the different reactivity of the metals and the dependence on surface orientation of the catalyst particles. Higher temperature and lower partial pressure yield smaller diameter MWNTs with fewer walls and a larger inner hollow core. The space velocity and thereby the H2 partial pressure in the reactor has been identified as the most important parameter for scale-up of the reactor.
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