COLL 574 |
| A combined IR, Raman and MS operando spectroscopic strategy was employed to examine the NOx storage and reduction process of supported Pt/Ba/K/Al2O3 catalysts in real time in the 25-400 oC temperature range and different environments (lean and rich gas compositions). Raman spectroscopy provided molecular structural information about the oxidation state of the supported Pt and formation of bulk crystalline nitrate and carbonate species. The complementary IR spectroscopy provided molecular structural information about the surface adsorbed NOx and COx species and the online mass spectrometer provided the real time product evolution from the catalytic bed. The platinum component was present as PtOx, indicated by Raman band at 500-600 cm-1, under lean conditions and metallic Pt under rich conditions. Exposure to NO2 flow resulted in both surface and bulk nitrate formation with the latter being accelerated in the presence of PtOx. Exposure to CO2 resulted in the formation of surface and bulk carbonates, IR bands at 1300-1500 cm-1 and Raman band at 1060 cm-1, respectively, which were partly depleted in the presence of NO2 flow. The NOx storage-reduction mechanism over supported Pt/Ba/K/Al2O3 catalysts will be discussed from these new fundamental molecular level insights. |
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Operando Spectroscopy of Working Catalysts
8:30 AM-11:45 AM, Thursday, 14 September 2006 Sir Francis Drake -- Windsor Room, Oral
Division of Colloid & Surface Chemistry |