A technique and equipment are provided for regenerating a potentially sulfur-burdened, noble metal catalyst (44) in a water gas shift reactor (150, 152, 154), which may be part of a fuel processing system (120) for a fuel cell power plant (110). An oxidant (91) is supplied to the reactor and catalyst during a period when the water gas shift reaction is terminated, and sulfur entities burdening the catalyst undergo an oxidation reaction to become SO2. The SO2 is then vented outside the system containing the reactor, as to the ambient. The oxidation reaction preferably occurs immediately upon the shift reaction being terminated to take advantage of the residual heat associated with the water gas shift reaction. Oxidant is conveniently admitted to the shift reactor and SO2 is vented from the reactor by appropriately-controlled valving that may work in combined alternation with the normal flow of process fuel through the shift reactor and fuel processing system.