OP-II-3

PP-I-3NOLINEAR PHENOMENA IN CATALYTIC REACTIONS WITH ABRANCH-CHAIN MECHANISM OF FORMATION OF ACTIVE CENTERSAndrianova Z.S., Ivanova A.N., and Barelko V.V.Institute of Problems of Chemical Physics, RAS, Chernogolovka, 142432 Russia,e-mail: ivanova@icp.ac.ruThis study continues a series of works [1–5] on the special features of instabilitymanifestations in exothermic heterogeneous catalytic reactions with nonlinearkinetics. Here we consider a model of a branched chain catalytic reaction C→ Bwhose kinetic is described by the schemeC + 2n →Cnn, (1)Cnn + n*→ B + 3n, (2)n →n*. (3)Here, stage (1) corresponds to the two-center adsorption of the initial reagent (C)from the gas phase on surface active centers (n), stage (2) is the formation of thefinal transformation product (B) accompanied by the multiplication of active centers(n* is the inactive center activated by the catalytic event), and stage (3) describes thereversible deactivation of surface active centers and restoration of their activity.The accepted physical model corresponds to a thin catalytic filament with a crossflow of reagents past it. Such a model not only simplifies analysis by using the onedimensionalapproximation but also corresponds to real conditions ofelectrothermographic experiments performed to study the dynamic characteristics ofheterogeneous catalytic transformations (see [6, 7]). The differential equationsdescribing the system under consideration have the formm ∂T/ ∂t= λ ∂2 2∂c/ ∂t= Dc∂ c / ∂x+ b / δ2 2∂n/ ∂t= Dn∂n / ∂x− 2K*∂n/ ∂t= D2 * 2∂ n / ∂x−∂cnnn*/ ∂t= Dcnn2T / ∂x∂2cnn2/ ∂x+ a / d (∑Qjj2( −K1n21nc + 3*K2cnnn22+ K1ncW− Kjnn+32− α( T − T )( c − c)c + β0*K2cn − K+ K n − Kcnnn*+3− *3n0))n + Kthe boundary conditions for the all the y = (T, c, n, n*, c nn ) components wereintroduced by setting the gradient at the ends of a catalytic element at zero.This model describes a hysteresis temperature dependence of reaction rate,domain structures appear because of local disturbances in the case of diffusioninstability of uniform stationary states under certain conditions for transfercoefficients, autowave transition processes are characterized by a “plateau” of zerofront velocities with the formation of standing waves.−3n*(4)223