The synthesis of carbon nanotubes (CNTs) on a cobalt-iron (Co-Fe) catalyst supported on a calcium carbonate (CaCO3) substrate, contained within a fluidized bed was investigated for the first time. CaCO3 supported catalysts, prepared using traditional wet impregnation techniques result in a soft and sticky powder requiring special arrangements to ensure satisfactory fluidization. A modified method developed using citric acid complex resulted in CaCO3 supported catalysts that can be classically fluidized without special arrangements. The issue of Fe3+ (aq) hydrolysis above its critical pH of similar to 3.5 was also addressed. A carbon yield consistently greater than 10 times the weight of the catalyst metal loading was obtained. Thermogravimetric analysis coupled with mass spectrometry showed a single peak centered on 575 degrees C, with no peaks below 400 degrees C, indicating that an insignificant quantity of amorphous carbon was present. Transmission electron microscopy verified that the products contained a large proportion of CNTs. (c) 2008 American Institute of Chemical Engineers.