Two-dimensional spatial resolution of concentration profiles in catalytic reactors by planar laser-induced fluorescence: NO reduction over diesel oxidation catalysts.

Planar laser-induced fluorescence (PLIF) enables noninvasive in situ investigations of catalytic flow reactors. The method is based on the selective detection of two-dimensional absolute concentration maps of conversion-relevant species in the surrounding gas phase inside a catalytic channel. Exemplarily, the catalytic reduction of NO with hydrogen (2 NO+5 H2 →2 H2 O+2 NH3 ) is investigated over a Pt/Al2 O3 coated diesel oxidation catalyst by NO PLIF inside an optically accessible channel reactor. Quenching-corrected 2D concentration maps of the NO fluorescence above the catalytic surface are obtained under both, nonreactive and reactive conditions. The impact of varying feed concentration, temperature, and flow velocities on NO concentration profiles are investigated in steady state. The technique presented has a high potential for a better understanding of interactions of mass transfer and surface kinetics in heterogeneously catalyzed gas-phase reactions.