The effect of thermal deactivation on CO oxidation over a Pt/Al2O3 monolith supported catalyst was investigated using IR thermography. Characterization of the fresh catalyst, via measurement of surface temperature versus time and axial position data, clearly demonstrated the expected evolution at reaction ignition of a reaction front that moves from the back to the front of the monolith and increases in intensity as is moves toward the inlet. Propagation of the reaction front occurred even after full conversion of CO into CO2 was achieved. Ultimately, the actual reaction was confined within a band of short depth relative to the full length of the monolith. The opposite was observed during extinction experiments. Propagation of the temperature wave and ignition/extinction events can be explained by competition between CO self-poisoning and temperature. As ignition moved toward the inlet position, a heat conduction wave was clearly observed, resulting in increased temperatures downstream that were not associated with any local reaction at those positions.

After a homogeneous, high-temperature treatment of the catalyst, higher ignition and extinction onset temperatures were observed. Furthermore, the speed of the reaction wave propagation decreased and therefore full conversion attainment with ignition onset took longer. In comparing data sets where similar conversions were obtained prior to and after degradation, it is apparent that the reaction zone is also wider after degradation. The conduction band intensity also decreased after the thermal degradation, although the upstream temperatures observed were similar when compared to the fresh catalyst.

Monitoring CO oxidation over the catalyst not only demonstrates the viability of the technique for reaction characterization as a function of axial position in a monolith-supported catalyst, but also demonstrates a spatially resolved analysis of thermal degradation effects. The latter observation can be used to evaluate/validate monolith channel catalyst models.

Extended Abstract Status: Not Uploaded