NOx adsorption on K and Ba loaded on zirconia-titania NSR catalysts: A comparative study by insitu and operando IR spectroscopy

by Hai P. Nguyen , Sandra Palma Del Valle and Olivier Marie

An intensive in-situ and operando IR study on NOx adsorption over potassium (K) loaded zirconia-titania NSR catalyst in comparison to a barium (Ba) loaded one is reported. Based on in situ IR experiments, NOx adsorption under heated environment was confirmed to favor potassium bidentate nitrate species rather than ionic nitrate species observed for Ba-loaded NSR catalyst (previously published). Complementary operando  IR experiments revealed different mechanisms for NOx adsorption over the two NOx storage materials (NSMs): initial simultaneous NOView the MathML source and NOView the MathML source formation over K loaded catalyst while over Ba-loaded one, NOView the MathML source is first accumulated before being converted to NOView the MathML source. Isotopic labelling in combination with operando experiments identified distinct dynamic behaviors regarding the exchange between nitrogen containing species on surface and in gas phase. This work provides beneficial inputs for advanced catalyst converter design, for example with zone-coated washcoat that contains more than one catalyst formulations.

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