III International Conference

PP-III-67INFLUENCE OF DIFFUSION, SIZE AND SHAPE OF CATALYST SURFACE ONREACTION RATEBykov V.I., Kiselev N.V.Moscow State Technical University, Moscow, RussiaKrasnoyarsk State University, Krasnoyarsk, RussiaE-mail: kiselevskii@rambler.ruDependence of mean reaction rate and amplitude of oscillations on solid catalyst surfaceupon its size and shape (plate, cylinder, sphere, thorus) was investigated.Simple schemes of heterogeneous catalytic reactions traditionally act as an objects forinvestigation of critical phenomena in chemical kinetics. In particular, oscillations of reactionrate, wave propagation processes and pattern formation were revealed for the first time onsimple models.system:We considered kinetic model corresponding to the «catalytic oscillator + diffusion»x&x&x&23= 2k= k= k24z−21 12z − kz − k−2−4kx2−11− kx2− k3x1xx .33x21x2,+ D z22( ∇ x − x ∇ z)where x1,x2, x3are the surface coverages of interim substances, z = 1−x1− x2− x3, k sandk − s are adsorbtion and desorbtion rate constants of stage s , D – diffusion factor.Differential equations system (1) was solved numerically with the next parameter values:k 1 = 2,5;k − 1 = 1;k2= 1;k −2= 01 , ; k3= 10;k4= 0,0675;k−4= 0,022 . If D = 0 then this modelcorresponds to the «catalytic oscillator» in oscillating mode. Boundary conditions were addedto equations system (1) depending on catalyst shape. Peculiarities of numerical integrationalgorithms for different catalyst shapes (plate, cylinder, sphere, thorus) were described in ourprevious papers. Stability of these algorithms is conditioned by t q ( Δh) D22,2(1)Δ ≤ , where Δ tis a step of integration by time scale,Δ h is a step of integration by spacial scale, q is amultiplier of order110 − . Two different kinds of initial conditions were considered: zero-filledand random-filled surfaces. It turned out that obtained results for sufficiently long processtime are not depend on choice of these conditions.593