Oxygen storage behavior of ceria-zirconia-based catalysts in the presence of SO2

This paper investigates the effect of the presence of SO2 in the dynamics of oxygen storage on ceria and ceria-zirconia. The introduction of SO2 under reaction conditions at T < 873 K negatively affects CO conversion under oscillating conditions on all the supports studied, owing to the formation of sulfate species. Deactivation is observed on all supports and activity is recovered only after desorption of SO2, which occurs at 950 < T < 1000 K, depending on catalyst composition (Ce/Zr ratio) and treatment atmosphere. The amount of sulfur adsorbed is higher over solid solutions, reaching a maximum with CexZr1-xO2 (0.5 < x < 0.68). However this does not adversely affect activity compared to ceria. In the presence of Rh and Pd, reactivation is favored under reaction conditions. More generally, it appears that the removal of sulfates is facilitated in reductive atmospheres (both hydrogen and CO) over mixed oxides. No differences are observed following regeneration under oxidizing conditions.