Oscillatory catalytic reactions Platinum

Ortho-para deuterium, 27 25, 50 Ortho-para hydrogen conversion, 27 23 Oscillatory catalytic reactions, 37 213-215, 271-272 see also Platinum catalytic CO oxidation on Pt(l 11) and Pt(llO) surfaces COj formation, 37 216-217 kinetic oscillation mechanism, 37 220-228... 

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 dynamic behavior of fixed-bed reactors has not been extensively investigated in the literature. The only reaction which received close attention was the CO oxidation over platinum catalysts. The investigations revealed interesting and complex dynamic behavior and have shown the possibility of oscillatory behavior as well as chaotic behavior (79-81). It is easy to speculate that more emphasis on the study of the dynamic behavior of catalytic reactions will reveal complex dynamics like those discovered for the CO oxidation over a Pt catalyst, for most phenomena are due to the nonmonotonicity of the rate process, which is widespread in catalytic systems. 

In a recent publication reviewing the status of research into intrinsic oscillations in solid-catalyzed reactions (l ), we emphasized the potential exploitation of combined theoretical and experimental studies of oscillatory behavior for obtaining new insights into catalytic reaction mechanisms and kinetics. In the present paper, we elaborate further on the subject of formulating and analyzing kinetic models which account for oscillatory behavior, and we present some new experimental information for the oscillatory oxidation of CO on a platinum foil. As in reference 1, the analysis here is applied to models describable by two first-order differential equations. The laboratory data reported were obtained from an isothermal gradientless CSTR of void volume h60 cm3 into which there was inserted a platinum foil of area 200 cm2. Continuous measurements were made of the CO2 concentration in the effluent stream. The experimental system is described in detail elsewhere (, . ... 

Now possibilities of the MC simulation allow to consider complex surface processes that include various stages with adsorption and desorption, surface reaction and diffusion, surface reconstruction, and new phase formation, etc. Such investigations become today as natural analysis of the experimental studying. The following papers [282-285] can be referred to as corresponding examples. Authors consider the application of the lattice models to the analysis of oscillatory and autowave processes in the reaction of carbon monoxide oxidation over platinum and palladium surfaces, the turbulent and stripes wave patterns caused by limited COads diffusion during CO oxidation over Pd(110) surface, catalytic processes over supported nanoparticles as well as crystallization during catalytic processes. 

---