The effect of sulfidation temperature on the catalytic activity of MoO3/CeO2-Al2O3 toward sulfur-resistant methanation was studied. The prepared catalysts were characterized by N-2 physisorption (BET), X-ray diffraction (XRD), Raman spectroscopy (RS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD and XPS results indicated that CeO2 was sulfided at sulfidation temperatures above 500 degrees C. During sulfidation at 500 degrees C or above, Ce3+ ions diffused into the catalyst, and/or Al3+ ions migrated to the surface of the catalyst. These two changes enhanced catalyst stability and decreased catalytic activity. The initial catalytic activity decreased as the sulfidation temperature increased. This decrease occurred for the following reasons: the decrease in BET surface area, the undesired sulfidation of CeO2 on the surface, and the crystallization of amorphous MoS2 to form MoS2 crystals. Finally, CeO2 and MoO3 sulfidation mechanisms were proposed for temperatures greater than 500 degrees C. (C) 2013 Elsevier B.V. All rights reserved.