290205 Investigation On the Effect of Co in Co-Promoted Pt-Ba/Al2O3 Nox Storage and Reduction Catalytic Converter Catalysts

Monday, October 29, 2012
Hall B (Convention Center )
Calvin Thomas1, Chris Digiulio2 and Michael D. Amiridis2, (1)Chemical Engineering, Auburn University, Auburn, AL, (2)Department of Chemical Engineering, University of South Carolina, Columbia, SC

A series of Co-promoted Pt-Ba/Al2O3 NOX storage and reduction (NSR) catalysts were prepared in order to understand the promotional effect that Co reportedly has on conventional Pt-Ba/Al2O3 NSR catalysts.  The catalysts were extensively characterized using atomic absorption spectroscopy (AAS), H2-O2 chemisorption, Brunauer-Emmett-Teller (BET) surface area measurements, x-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscopy (SEM).  The NOX storage capacity was measured using mass spectroscopy.  In situ Fourier transform infrared (FTIR) spectroscopy was used to identify the types of surface species present during both storage and reduction.  It was found that adding Co significantly improved the storage capacity for catalysts containing low Pt weight loadings (0.25 wt.%) and slightly improved storage for catalysts with higher Pt weight loading (1 wt.%), especially at lower temperatures (e.g., 150 – 250 °C).  Co was also observed to catalyze the transition from nitrites to nitrates during storage.  During reduction, isocyanate (NCO) species were observed on all of the samples investigated, but the Pt-only containing catalysts generally formed NCO species in higher concentrations.  Subsequent reactivity measurements confirmed that the surface NCO species formed on the Pt-only containing catalysts were more reactive towards NO and O2 mixtures than surface NCO species formed on Co-promoted samples.

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