Kinetic Study of Carbon Nanotubes Synthesis by Fluidized Bed Chemical Vapor Deposition

Multi-walled carbon nanotubes (MWCNTs) have been produced with high selectivity by fluidized bed catalytic chemical vapor deposition from ethylene oil FelAl(2)O(3) catalysts. The influence of operating parameters such as deposition duration, temperature, ethylene and hydrogen partial pressures, and iron loading oil MWCNT productivity, process selectivity, characteristics of final powders, and chemical composition of the outlet gases has been analyzed. Using gas phase chromatography, methane and ethane have been detected, whatever are the conditions used. Between 650 and 750 degrees C, no catalyst deactivation occurs because nucleation remains active all along the synthesis, thanks to the explosion of the catalyst grains. Above 650 degrees C, ethane itself produces MWCNTs, whereas methane does not react in the temperature range, 550-750 degrees C. The formation of MWCNTs induces marked bed expansions and sharp decreases of grain density. Apparent kinetic laws have been deduced from the collected data. The apparent partial orders of reaction for ethylene, hydrogen, and iron were found to be 0.75, 0, and 0.28, respectively. (c) 2008 American Institute of Chemical Engineers AIChE J. 55: 450-464, 2009