Sales-Turner-Maple model

The abstract models can be divided into two categories, each of which can be further subdivided into three classes (Fig. 5). Some of the models consist of coverage equations only, and these models will be called surface reaction models. The remaining models use additional mass and/or heat balance equations that include assumptions about the nature of the reactor in which the catalytic reaction takes place (the reactor could be simply a catalyst pellet). These models will be called reactor-reaction models. Some of the models mentioned under the heading surface reaction models also incorporate balance equations for the reactor. However, these models need only the coverage equations to predict oscillatory behavior reactor heat and mass balances are just added to make the models more realistic [e.g., the extension of the Sales-Turner-Maple model (272) given in Aluko and Chang (273)]. Such models are therefore included under surface reaction models, which will be discussed first. 

Fig. 6. General representations of heterogeneous oscillatory mechanisms, (a) Buffer-step model (b) coverage-dependent activation energy (c) empty-site model (d) Sales-TUrner-Maple model (e) Pt(lOO) phase transition model (f) Dagonnier model (g) blocking/ reactivation model (h) bulk-phase transition model.

Vayenas et al. (J89) developed a model for ethylene oxidation on Pt based on solid-state electrolyte measurements that resembles the Sales-Turner-Maple model described in Section IV,A. However, Vayenas et al. balanced gas-phase concentrations and considered the surface coverages of only two species, namely active and inactive oxygen. Ethylene was assumed to react very rapidly, thus never reaching a significant surface coverage. This model semiquantitatively reproduced the experimentally observed behavior. 

---