Effect of the particle size and the active phase composition in CoFe/γAl2O3 catalyst on the multiwalled carbon nanotube production

Abstract Iron-cobalt supported on alumina catalysts with different particle size, metal loading and atomic ratio composition are investigated in the catalytic reaction decomposition of ethylene at 700°C to produce multi-walled carbon nanotube (MW-CNT) and hydrogen. The catalysts were characterized by surface area, XPS and XRD techniques. The quality of the MW-CNT produced was determined by thermo- gravimetric (TG) and transmission electron microscopy (TEM) techniques. Our result shows that the MW-CNT production decreases for particles size > 70 μm whereas for particles sizes 2 O 3 , Co 3 O4 and a Co x Fe y O z mixed phase for all Co-Fe/γAl 2 O 3 catalyst compositions. We suggest that the latter species are responsible for the higher MW-CNT productivity of the CoFe/γAl 2 O 3 catalyst.