Sulfur poisoning and NH3 regeneration of Pt/Al2O3: oxidations of SO2, NH3, NO and C3H6 as probe reactions

The impact of SOx (x = 2, 3) on the activity of a model diesel oxidation catalyst (DOC: Pt/Al2O3) is examined for the oxidations of sulfur dioxide (SO2), nitric oxide (NO), and propylene (C3H6). Flow reactor studies conducted of the Pt/Al2O3 washcoated monolith before and after sulfation quantify the detrimental deactivation. Subsequent exposure of the poisoned catalyst to NH3 without and with O-2 enables the assessment of its effectiveness as a regenerant. A combination of steady state reaction, temperature programmed desorption (TPD) and reaction (TPR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are conducted to characterize the poisoning and regeneration processes. Mechanistic explanations are proposed consistent with DRIFTS-identified surface species. The findings suggest a potential mitigation strategy for restoring the activity of Pt/Al2O3 in diesel emission control. The effectiveness of the activation restoration strategy is in the order of NH3 oxidation > SO2 oxidation > C3H6 oxidation > NO oxidation.