Mechanism of NO reduction by CO over Pt/SBA-15

• Pt/SBA-15 is active for CO + O2 and CO + NO reactions, but not for NO disproportionation.
• The change in isocyanate surface concentration correlates well with the CO + NO activity of the catalyst.
• Isocyanates are intermediates in the CO + NO reaction over Pt/SBA-15 catalyst
• A mechanism for CO + NO reaction over Pt/SBA-15 is proposed.

The mechanism of the CO + NO reaction catalyzed by Pt/SBA-15 was studied via independent investigations of CO oxidation and NO disproportionation. Below 400 °C, both CO + O2 and CO + NO reactions approach 100 % conversion, while the catalyst shows negligible activity for NO disproportionation. These results suggest that CO oxidation by atomic oxygen arising from NO dissociation is not a major route for CO2 formation in the CO + NO reaction. In situ IR spectra reveal the formation of isocyanates (NCO−) adsorbed on silica. Their surface concentration changes with the extent of the CO + NO reaction. A mechanism is proposed in which isocyanates are reaction intermediates.

Two possible reaction routes for the CO + NO reaction conducted on a Pt/SBA-15 catalystFigure optionsDownload as PowerPoint slide