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:
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.
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.
sulfur poisoning, thermal deactivation and BaCO3 formation in lean NOx 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.