Oscillations on individual catalytic pellets in a packed bed: CO oxidation on Pt/Al2O3

Modeling of Three-Way-Catalyst Monolith Converters with Microkinetics and Diffusion in the Washcoat

“…Finally monotonic outlet CO concentrations are observed. Thus, the above kinetic model based on nonstationary kinetics predicts a qualitatively similar evolution of outlet conversions as sequences of regimes observed in experiments. , …”

“…Experiments on individual catalytic Pt/γ-Al 2 O 3 pellets with transport effects for CO oxidation on Pt/γ-Al 2 O 3 were performed in our laboratory in the late 1980s. Both synchronous periodic and aperiodic oscillations of CO, CO 2 , and temperature on individual pellets were observed . A reproducible transition from simple periodic oscillations via a sequence of period-doubling bifurcations to deterministic chaos was also observed …”

Spatiotemporal patterns in catalytic reactors

“…When the surface was conquered by these traveling waves, the spatial average of the reaction became constant in time, and thus the impact of global coupling was reduced. Kapicka and Marek (1989) observed complete synchrony between pellets in a high-recirculation packed-bed reactor, during CO oxidation over supported Pt catalyst; the amplitudes and form of oscillations differed from one pellet to another. Temporal patterns became more complex at higher temperature; significant concentration gradients existed at low recycle ratios, but the pellets were synchronized.…”

“…The observation of a glowing Pt wire during ammonia oxidation was used to follow the front motion (Barelko et al, 1978). Thermal patterns in catalytic reactors have long been monitored by an array of thermocouples (e.g., Kapicka and Marek, 1989;Onken and Wolf, 1988;Jaeger et al, 1986) or by a moving thermocouple in a thermowell (Adaje and Sheintuch, 1990). Thermocouple probing is satisfactory for portraying one-dimensional large-scale patterns (as in the fixed-bed, Dvorak et al, 1993), but will not give a coherent picture in two-dimensional systems and cannot be used for small-scale measurements or thin wires (Chen et al, 1993;.…”

Exact distributed kinetic Monte Carlo simulations for on-lattice chemical kinetics: lessons learnt from medium- and large-scale benchmarks

“…obtain fundamental understanding), but also by the potential benefits of controlling, improving, and/or engineering novel chemical systems for technologies of practical interest. For instance, CO oxidation on Pt catalysts in surface science experiments [25] and in reactors [26][27][28], partial oxidation of methane on Pd catalysts [29], N 2 O decomposition on Cu-ZSM5 [30], and the NO reduction by CO, H 2 or NH 3 on Pt surfaces [31,32] have all been shown to exhibit oscillations that may markedly affect activity or selectivity. In general, it has been argued that oscillations and spatio-temporal pattern formation may lead to potentially dangerous operating regimes in industrial reactors, but when properly managed and effectively controlled they could lead to enhancements in the conversion [33], thereby motivating fundamental studies to better understand such phenomena.…”