Spatially and Temporally Resolved Measurements of NO Adsorption/Desorption over NOx-Storage Catalyst

The two-dimensional (2D) temporal evolution of the NO-concentration over a NOx-storage catalyst is investigated in situ with planar laser-induced fluorescence (PLIF) in an optically accessible parallel wall channel reactor. Signal accumulated phase-correlated 2D-recordings of repetitive adsorption/desorption cycles are obtained by synchronizing the switching of the NO gas flow (on/off) with the laser and detection system, thereby significantly increasing the signal-to-noise ratio. The gas compositions at the reactor outlet are additionally monitored by ex-situ analytics. The impacts of varying feed concentration, temperature and flow velocities are investigated in an unsteady state. Transient kinetics and the mass transfer limitations can be interpreted in terms of the NO concentration gradient changes. The technique presented here is a very useful tool to investigate the interaction between surface kinetics and the surrounding gas flow, especially for transient catalytic processes.