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

Abstract

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 smallamplitude 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 nonun$orm states existed mainly for feed conditions for which the only uniform state was an extinguished one.

Temperature Fronts and Patterns in Catalytic Systems

“…Mayer's (1914) measurements of rotating electrical pulses in ring-shaped jellyfish tissue probably represents the first utilization of this advantage. Temperature patterns were observed during the oxidation of hydrogen on metallic and supported nickel catalysts (Graham et al, 1993a;Somani et al, 1996;Somani et al, 1997b) as well as carbon monoxide oxidation on metallic Pt (Yamamoto et al, 1995) and supported Pd rings (Liauw et al, 1997). Concentration patterns on a thin Pt ring were observed by Graham et al (1994) during the oxidation of carbon monoxide.…”

Experiments on arrays of globally coupled chaotic electrochemical oscillators: Synchronization and clustering

“…21 Such coupling can have a strong role in altering pattern formation. 22 In electrochemical systems a nonlocal coupling among reactive sites arises through the electric field; potential changes at some location are transmitted rapidly to other locations. [23][24][25][26][27] This coupling is long-range but is not global because its effect dies out with increasing distance.…”

Noise induced oscillations and coherence resonance in a generic model of the nonisothermal chemical oscillator

“…It should be pointed out at this point that exothermic chemical oscillators have been extensively studied in heterogeneous catalytic systems, e.g. CO and NH 3 oxidation on Pt and Pd464748.…”