Abstract

Sulfur deactivation and regeneration behavior of the Pd/Al₂O₃ catalyst has been investigated via experimental characterization and density functional theory (DFT) simulations. During the sulfur exposure, PdO crystallites grow slightly while bulk Al₂(SO₄)₃ forms on the support. DFT calculations indicate that SOₓ species interact strongly with the catalyst surface making it chemically inactive in agreement with the experimental results. During the regeneration treatment (CH₄ conditions), PdO particles reduce, Al₂(SO₄)₃ is partially removed, and the activity for CH₄ conversion is increased. No full recovery can be observed due to remaining Al₂(SO₄)₃, the formation of encapsulating sulfur species, and the partial reduction of PdO particles. To reoxidize Pd, the catalyst is further regenerated (O₂ conditions). The resulting CH₄ conversion is at the same level than with the regenerated catalyst. Thus, a small amount of Al₂(SO₄)₃ appears to have a stronger effect on the performance than the state of Pd.