Experimental and numerical investigation of NO oxidation on Pt/Al₂ O₃- and NOₓ storage on Pt/BaO/Al₂ O₃-catalysts

Planar laser-induced fluorescence with laser synchronized flow control is employed as a non-invasive in situ technique to investigate a NOₓ storage catalyst, especially to grant a deeper insight into the reaction dynamics and its interaction with mass transfer. In addition to visualizing the spatial and temporal NO evolution over a Pt/BaO/Al₂O₃ catalyst, the spatially resolved NO distribution over a Pt/Al₂O₃ catalyst in the steady-state is measured to understand the oxidation of NO to NO₂ as a precursor step of NOₓ storage. The experimental results are compared with corresponding numerical simulations using transient one- and two-dimensional reactor simulations with detailed surface reaction mechanisms. The thermodynamic equilibrium for NO oxidation over Pt/Al₂O₃ approaches between 623 K and 723 K, as a reduced conversion is observed at a higher temperature. The NOₓ storage on the Pt/BaO/Al₂O₃ catalyst decreases with time, which is partly due to the reduced storage capacity, but also strongly limited by the NO oxidation rate.