The oxidation of carbon monoxide on platinum

In addition to kinetic interpretations such as those mentioned in the previous sections, three different types of explanation have been proposed. Scott and Watts (1981) have suggested a vital involvement of boundary layer films, allowing for considerable depletion of the bulk gas-phase concentrations of the reactants close to the catalyst. In the work on single crystals, Ertl 

In many other cases it is not at all clear that these exothermic reactions are operated in such a way that the system can remain isothermal. Self-heating and hence thermal feedback routes can be expected to have a strong autocatalytic effect on the reaction, perhaps in addition to chemical mechanisms. Recent modelling invoking cellular automata (Jaeger et al. 1985) has been to some extent successful at matching qualitatively many of the rather exotic responses which have been observed experimentally. 

and Yablonskii, G. S. (1981). Simplest model of catalytic oscillator. React. Kinet. Catal. Lett., 16, 377-81. 

Cameron, P., Scott, R. P., and Watts, P. (1986). The oxidation of carbon monoxide on a platinum catalyst at atmospheric pressure. J. Chem. Soc. Faraday Trans I, 82, 1389-403. 

Eigenberger, G. (1978). Kinetic instabilities in heterogeneously catalyzed reactions I. Chem. Eng. Sci., 33, 1255-61. 

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Watanabe M, Motoo S. 1975a. Electrocatalysis by ad-atoms. Part in. Enhancement of the oxidation of carbon monoxide on platinum by mthenium ad-atoms. J Electroanal Chem 60 275-283. 

The use of equation (3.2) to study the behaviour of catalysts is known as solid electrolyte potentiometry (SEP). Wagner38 was the first to put forward the idea of using SEP to study catalysts under working conditions. Vayenas and Saltsburg were the first to apply the technique to the fundamental study of a catalytic reaction for the case of the oxidation of sulfur dioxide.39 Since then the technique has been widely used, with particular success in the study of periodic and oscillatory phenomena for such reactions as the oxidation of carbon monoxide on platinum, hydrogen on nickel, ethylene on platinum and propylene oxide on silver. 

The review paper by Razon and Schmitz [87] on bifurcation, instability and chaos for the oxidation of carbon monoxide on platinum. 

The papers of Wicke and Onken [88] and Razon et al. [89] which give different views on the almost similar dynamics observed during the oxidation of carbon monoxide on platinum. Wike and Onken [88] analyze it as statistical fluctuations while Razon et al. [89] analyze it as chaos. Later, Wicke changes his view and analyzes the phenomenon as chaos [90]. 

Spiral waves also arise in the oxidation of carbon-monoxide on platinum surfaces [10]. In 1972 they have been discovered by Winfree [79] in the photosensitive Belousov-Zhabotinsky (BZ) reaction, see for recent investigations for example [83, 84, 87]. Both reactions are studied in the SFB 555. The classical BZ reaction is a catalytic oxidation of malonic acid, using bromate in an acidic environment. Experimentally it exhibits well reproducible drift, meander and chaotic motions of the spiral wave and its tip. 

The simplest mechanism for interpreting critical phenomena in heterogeneous catalysis is the Langmuir adsorption mechanism, also referred to as the Langmuir-Hinshelwood mechanism. This mechanism includes three elementary steps (1) adsorption of one type of gas molecule on a catalyst active site (2) adsorption of a different type of gas molecule on another active site (3) reaction between these two adsorbed species. For the oxidation of carbon monoxide on platinum, this mechanism can be written as follows ... 

Watanabe, M. and Motoo, S. (1975). Electrocatalysis by Ad-atoms Part III. Enhancementof the Oxidation of Carbon Monoxide on Platinum by Ruthenium Ad-atoms, J. Electroanal. Chem., 60, pp. 275-283. 

One of the objectives of this book is to demonstrate how the overall reaction rate of a catalytic reaction can be predicted once the rate constants and equilibrium constants of the elementary reaction steps are known. Such data can be obtained from model experiments, often in surface science, or from theoretical calculations. The ammonia synthesis was among the first catalytic reactions for which the rate was predicted under high pressure conditions. This was a remarkable success, as the calculation involved an extrapolation of data obtained under vacuum over a pressure interval of ten orders of magnitude. Here the effective rate constant of a less complex reaction is derived, the oxidation of carbon monoxide on platinum. We will use the reaction mechanism of Scheme (6.1) and label rate and equilibrium constants according to the number of the elementary steps in (6.1). 

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