Spatially resolved in situ measurements of transient species breakthrough during cyclic, low-temperature regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

We employed a new experimental technique known as spatially resolved capillary-inlet mass spectrometry (SpaciMS) to observe the evolution of multiple species inside the channels of a monolithic NOx storage-reduction (NSR) catalyst. The NSR material consisted of a Pt/K/Al2O3 washcoat deposited inside cordierite monolith channels. Spatially and temporally resolved measurements were made over the monolith length in a bench flow reactor during fast cycling between synthetic lean and rich environments at 200 and 300 °C. Regeneration was found to be very efficient at 300 °C regardless of whether pure H2, pure CO, or mixtures of H2 and CO were employed. At 200 °C, CO was noticeably less effective than H2. We conjecture that at 200 °C CO may be inhibiting the regeneration process through its strong adsorption on Pt. Generation of H2 by water-gas shift was seen at 300 °C but not at 200 °C.