The activity of a bulk molybdenum carbide catalyst for the steam (SR) and oxidative-steam reforming (OSR) of hexadecane has been studied with and without the presence of aromatic coke precursors and sulfur compounds. It is shown that this catalyst can be stable under very low steam:carbon ratios at temperatures as low as 885 degrees C under OSR conditions, and 965 degrees C under SR conditions. Using benzo-thiophene as a model sulfur compound at concentrations as high as 500 ppmw, the degree of deactivation was found to be dependent on the sulfur concentration but was minimal at concentrations below 100 ppmw. Experiments confirmed that the sulfur poisoning is reversible and characterization studies suggested the formation of sulfur entities, which lead to carbide oxidation and subsequent coking. There was minimal effect of the aromatic species on the catalyst stability. (c) 2005 Elsevier B.V. All rights reserved.