The deactivation by sulfur and regeneration of a model Pt/Ba/Al2O3 NO, trap catalyst is studied by hydrogen temperature programmed reduction (TPR), X-ray diffraction (XRD), and NO, storage capacity measurements. The TPR profile of the sulfated catalyst in lean conditions at 400 degrees C reveals three main peaks corresponding to aluminum sulfates (similar to 550 degrees C), "surface" barium sulfates (similar to 650 degrees C) and "bulk" barium sulfates (similar to 750 degrees C). Platinum plays a role in the reduction of the two former types of sulfates while the reduction of "bulk" barium sulfates is not influenced by the metallic phase. The thermal treatment of the sulfated catalyst in oxidizing conditions until 800 degrees C leads to a stabilization of sulfates which become less reducible. Stable barium sulfides are formed during the regeneration under hydrogen at 800 degrees C. However, the presence of carbon dioxide and water in the rich mixture allows eliminating more or less sulfides and sulfates, depending on the temperature and time. The regeneration in the former mixture at 650 degrees C leads to the total recovery of the NOx storage capacity even if "bulk" barium sulfates are still present on the catalyst. (c) 2005 Elsevier B.V. All rights reserved.