Thermal imaging of breathing patterns during CO oxidation on a Pd/glass cloth

Infrared (IR) thermography studies of oscillatory behavior during catalytic oxidation of CO over Pd supported on a glass-fiber catalytic cloth were conducted in a continuous reactor with feed flowing perpendicular to and through the disk-shaped catalyst. Typical thermograms of sustained patterns exhibit a hot spot that expands and contracts continuously (a breathing pattern), in a temporal pattern that matched the oscillations in exit CO2 concentration. The oscillations were of the complex relaxation type, with fast (1-min) oscillations superimposed on the active phase of the long (10-60-min) cycle. The change in the number of these smaller peaks, with a varying parameter, corresponds to a period-adding scenario. A model based on a published kinetic (isothermal) oscillator for this reaction, coupled with a solid-phase enthalpy and gas-phase mass balances, predicts these main features of the pattern. The novelty of these experimental results lies in the pattern, which is well defined and amenable to a systematic mathematical modeling, in the short period of the fast oscillations, as well as in the catalyst geometry, a disk-shaped cloth. (C) 2004 American Institute of Chemical Engineers