Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-9CHAOTIC DYNAMICS IN THE THREE-VARIABLE KINETIC MODELOF CO OXIDATION ON PLATINUM GROUP METALSE.A. Lashina, N.A. Chumakova, A.I. Boronin, G.A. Chumakov*Boreskov Institute of Catalysis SB RAS, Novosibirsk, 630090 Russiae-mail: iea78@mail.ru, chum@catalysis.ru*Sobolev Institute of Mathematics SB RAS, Novosibirsk, 630090 Russia,e-mail: chumakov@math.nsc.ruThe most widely studied heterogeneous catalytic reaction is CO oxidation on the metalsof platinum group. In particular, some conditions for such nonlinear effects as steady statemultiplicity, oscillations, and chaotic dynamics were described. In many cases, the kineticmodels, describing the complex irregular oscillations of reaction rate, have a large number ofvariables and parameters. One of the effective methods for analysis of nonlinear dynamics isthe separation of fast, moderate and slow motions in the model under consideration [1]. Thenthe dynamics of the whole system is determined by the structure of limit sets of thesubsystems of both fast and moderate motions.Using the hierarchical method, we have studied the scenarios of rise of chaotic dynamicsfor the CO oxidation reaction in the framework of a rather simple kinetic model that describesthe behavior of the dimensionless concentrations of CO (x) and oxygen (y) absorbed on thecatalyst surface, as well as the dynamics of the concentration of oxygen embedded into thesubsurface metal layer (z):x = K −x− y −K x− K xy,'1(1 )−13y' = 2 K (1 −x− y)−K xy,22 3z' = K y(1 −z)− K xz.4 5The assumptions on the reconstructive properties of the catalyst surface are as follows:1. A surface modification occurs and the activation energy of the interaction between theadsorbed species sharply increases when the adsorbed oxygen concentration y exceedssome critical value.2. A surface reconstruction occurs and the constant of oxygen adsorption decreases whenthe embedded oxygen concentration z exceeds some critical value.3. Oxygen and CO adsorption and interaction between them are faster then the oxygenembedding and the interaction between the embedded and adsorbed oxygen, i.e., z is aslow variable.42