Oscillating temperature pulses during CO oxidation on a Pd/Al2O3 ring

Back-and-forth-moving temperature fronts separating regions with high and low temperatures (amplitudes up to 100 K) formed on a Pd on alumina ring during the atmospheric oxidation of carbon monoxide. The back-and-forth front movement reflects the intrinsic nonuniformity of the catalytic system and the impact of global coupling. The ignition and extinction fronts usually moved at different velocities, in agreement with theoretical predictions. Complex spatiotemporal patterns were observed due to small-amplitude temperature fronts that moved on the high-temperature region at a much higher velocity than the high-amplitude fronts. The qualitative motion features were affected by changes in the excess oxygen concentration. The nonuniform states existed mainly for feed conditions for which the only uniform state was an extinguished one.