381327 Pattern Formation and Dynamics of a Model of Simultaneous Oxidation and Reduction in Three-Way Catalytic Converters Involving Cross-Flow

Wednesday, November 19, 2014: 3:35 PM
304 (Hilton Atlanta)
Martin Kohout and Igor Schreiber, Department of Chemical Engineering, Institute of Chemical Technology, Prague, Prague 6, Czech Republic

We present various modes of spatiotemporal dynamics occurring in a reaction-diffusion-convection model of a cross-flow tubular catalytic reactor involving a detailed model of the three-way catalytic oxidation of carbon monoxide and hydrocarbons and simultaneous reduction of nitrogen oxides. Under the assumption of isothermal operation the kinetics are sufficiently complex to possess several sources of  kinetic rather than thermokinetic autocatalysis and are able to support sustained oscillations and patterns. For convenience, the three-way system is split into two major subsystems, the oxidation of CO2 & C2H2 (a representative of hydrocarbons), and the oxidation of CO2 & reduction of NO.  These two basic subsystems are closely examined for possible dynamic instabilities by using the stoichiometric network analysis and the classification of chemical oscillators. We find that the instabilities are provided by specific subnetworks which provide for the bistability and oscillatory dynamics under the assumption of a spatial homogeneity (lumped system). Bifurcation analysis is applied to identify these basic dynamical modes in a the lumped system and to construct bifurcation diagrams in the inlet temperature – inlet oxygen concentration plane. Then the two basic subsystems are examined in the  tubular catalytic reactor with longitudinal diffusive/convective transport and with cross-flow. Thus reactants are assumed to be supplied both at the inlet and along the reactor. Patterns including nonhomogeneous steady states, travelling waves and  spatiotemporal chaos occur. We examine how these patterns are related to the specific kinetic features of the two distinctly different subsystems and conclude that there are both kinetics independent and kinetics specific features of the patterns.

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