Regeneration of Sulfur Poisoned Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 and Pd–Pt/Al2O3 Methane Oxidation Catalysts
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The poisoning of Pd–Pt/Al2O3 and Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 methane oxidation catalysts by SO2 was studied under conditions typical for lean burn gas engines. Regeneration of sulfur-poisoned catalysts was achieved by applying rich conditions at 500 and 550 °C. The presence of NOx resulted in a slower deactivation rate. While Pd–Pt/CeO2–ZrO2–Y2O3–La2O3 showed a superior catalytic activity, durability and regeneration ability compared to Pd–Pt/Al2O3 under NOx-free reaction conditions, its reactivation by a rich treatment was strongly inhibited if NOx was present during the aging and regeneration process. Operando X-ray absorption spectroscopy (XAS) was used to monitor the evolution of Pd and Pt during poisoning and regeneration. The studies show the formation of PdS and metallic Pd during reactivation of Pd–Pt/Al2O3, followed by transition to PdO after changing to lean reaction gas mixture. On the other hand, Pd species supported on CeO2–ZrO2–Y2O3–La2O3 could not be reduced under rich conditions and no regeneration occurred.
KeywordsMethane oxidation Emission control Sulfur poisoning Pd–Pt catalyst Catalyst deactivation Operando spectroscopy
We acknowledge SOLEIL for provision of synchrotron radiation facilities and we would like to thank S. Belin and V. Briois for assistance in using beamline ROCK. This work was supported by a public grant overseen by the French National Research Agency (ANR) as part of the “Investissements d’Avenir” program (reference ANR-EQPX-45). The authors thank the DFG (High-Output Catalyst Development Platform, INST 121384/16 − 1). Dr. G. Cavusoglu is acknowledged for the support during the XAS-experiments, A. Deutsch is acknowledged for the BET-measurements and maintenance of the High-Output Catalyst Development Platform. P. Lott gratefully thanks the “Fonds der Chemischen Industrie” (FCI) for financial support.
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