Spatially-Resolved Temperature and Gas Species Changes in a Lean-Burn Engine Emissions Control Catalyst

Infrared thermography and spatially resolved capillary inlet mass spectrometry (SpaciMS) have been used to characterize propylene oxidation reactions occurring along a Pt/Al2O3 monolith-supported catalyst before and after heterogeneous thermal degradation, with the heterogeneous aging being more representative of real-world conditions. The combined techniques clearly show reaction location and, therefore, catalyst use and how these change with thermal aging. Following the inhomogeneous aging, the reaction zones at steady state were broader and located farther into the catalyst relative to those observed with the fresh catalyst. In addition, the time for the temperature and concentration waves to travel through the catalyst during back-to-front ignition increased. These effects were more pronounced with lower propylene concentrations. Such trends could not be detected on the basis of standard catalyst-outlet measurements. The light-off behavior was also impacted by the aging, resulting in complex changes to the temperature front propagation, depending on the propylene concentration.