Steam reforming of n-dodecane on La-Ni/gamma-Al2O3 catalysts was investigated at a relatively low temperature (773 K) to elucidate the catalytic behavior at the inlet of a practical reformer. The addition of lanthanum to the Ni/gamma-Al2O3 formulation completely suppressed carbon deposition, which otherwise occurs to a significant extent on unmodified Ni/gamma-Al2O3. Modification with La also enhanced the initial turnover rates of hydrogen formation. The La-Ni/gamma-Al2O3 catalysts, however, deactivated with increased time-on-stream at a high steam-to-carbon ratio of 3.5, because of oxidation of the active Ni metal. Reduction at 873 K almost fully regenerated the catalytic activity, indicating that the deactivation was not primarily a result of sintering or carbon deposition, but was due to the oxidation of active Ni metal. (C) 2010 Elsevier B.V. All rights reserved.