Ethanol decomposition was studied over Ni/Al2O3 catalysts with different Ni loadings (10-90 mol%) at temperatures between 500 and 800 degrees C to produce hydrogen and multi-walled carbon nanotubes (MWCNTs) at the same time. The hydrogen production increased with increasing temperature and Ni loadings. However, both the quality and the quantity of the nanotubes formed at the relatively high temperatures of 700 and 800 degrees C decreased due to sintering of the Ni particles. The Ni (80 mol%)/Al2O3 Was the most effective catalyst for ethanol decomposition into hydrogen (the maximum H-2 yield of 83%) and MWCNTs (the maximum deposited yield of 80%) at 600 degrees C. Carbon nanofibers (CNFs)and MWCNTs were observed simultaneously on Ni (90 mol%)/Al2O3 at 500 degrees C. Several possible reactions also were proposed to explain ethanol decomposition to produce hydrogen and carbon (including nanotube), etc., at the same time. (C) 2008 Elsevier B.V. All rights reserved.