Detailed kinetic modeling study of NOx oxidation and storage over Pt/Ba/Al2O3 catalysts

Nikola  Rankovic, IFP

The nitrogen oxide storage-reduction (NSR) concept is doubtlessly one of the most promising technologies for reducing NOx emissions from lean-engine exhaust. The modeling effort in he present work is focusing on NO to NO2 oxidation over a Pt/Al2O3 model catalyst and NOx storage over Pt/Ba/Al2O3. A unique detailed NO oxidation kinetic model was conceived and validated over a wide range of experimental data. The detailed oxidation model was further exploited for developing a Langmuir-Hinshelwood-type rate expression. A detailed kinetic scheme for NOx storage was also validated against several experimental data. The detailed oxidation and storage kinetic models were then successfully coupled and species spillover between the noble metal and the storage material was accounted for. The variety of literature data allowed validating the kinetic scheme using a monolith and a fixed-bed reactor models. Both the detailed and the global kinetic model reproduce well the experimental NO conversion profiles obtained over Pt/Al2O3. NOx profiles calculated with the coupled oxidation-storage model are also in agreement with the experimental findings for washcoated monolith reactors and fixed-bed catalytic reactors. Reaction pathway analyses and sensitivity studies were performed to provide a more comprehensive insight into the system behavior and identify the critical steps.

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