Catalytic removal of NO from post-flame gases in low pressure stagnation-point flames over platinum

Experimental NO profiles in H₂/O₂/NH₃ stagnation point flames over platinum substrates are obtained with laser-induced fluorescence for a range of flame equivalence ratios and substrate temperatures. This study generates baseline data against which comprehensive gas-phase and surface chemical models of NO destruction can be compared. The experimental profiles are compared with the predictions of a one-dimensional stagnation flow model that includes full gas-phase chemistry, multicomponent transport, and detailed surface chemistry. A baseline surface chemistry mechanism, assembled by using conventional H/O heterogeneous chemistry and NO adsorption and dissociation followed by N₂ desorption, provides good agreement with the experimental results for only a limited range of operating conditions. At low temperatures (425 K), the mechanism underpredicts NO removal, while at high temperatures (940 K) and fuel-lean conditions (Φ = 0.7) the mechanism overpredicts NO destruction. Addition of NH₂ and N₂O production to the surface mechanism does not improve the level of agreement. However, consideration of the reconstruction of the platinum surface at high temperatures tends to shift the predicted profiles closer to those observed in the experiment for the high temperature cases.