Raman Studies of Automotive Catalyst Deactivation

Dairene Uy; Ann E. O'Neill

doi:10.4271/2006-01-0409

2006-04-03

Raman Studies of Automotive Catalyst Deactivation 2006-01-0409

Catalyst durability is a major concern in automotive exhaust gas treatment, and can be affected by chemical and thermal history. In this work, applications of in situ UV and visible Raman spectroscopy to a variety of catalyst deactivation issues are demonstrated:

a)
identification and characterization of CePO₄ in three-way catalysts. CePO₄ forms from the interaction of phosphorus in engine oil additives with the catalyst washcoat. It affects oxygen storage and decreases catalyst conversion efficiency.
b)
thermal deactivation in Pd/ceria-zirconia catalysts. A compressive strain on palladium oxide as indicated by its Raman shift can serve as a diagnostic for a thermally-deactivated catalyst and thus the unavailability of the Pd for catalysis.
c)
sulfur poisoning, thermal deactivation and BaCO₃ formation in lean NO_x traps (LNT). Spectral features demonstrate sulfation of LNT components, differences in fresh and thermally-aged Pt/Ba/Al₂O₃ which are consistent with results from activity and chemisorption measurements, and possible correlations of BaCO₃ formation to catalyst activity.

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Raman Studies of Automotive Catalyst Deactivation 2006-01-0409

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