Experimental and numerical investigation of NO oxidation on Pt/Al2O3- and NOx storage on Pt/BaO/Al2O3-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.