Dynamical behavior of reaction-transport processes in a three-way catalytic converter, where catalytic oxidation of carbon monoxide and hydrocarbons occurs simultaneously with reduction of nitrogen oxides, can be in the simplest approximation described by a model of an isothermal stirred flow-through reactor where transport phenomena are largely neglected but detailed kinetics involving elementary adsorption and chemical steps are considered. Then the stoichiometric networks analysis can be used when looking for an answer to whether there exist kinetically, rather than thermokinetically, driven dynamical instabilities and what part of the mechanism is responsible for nonlinear phenomena such as multiple steady states and oscillations. This approach elucidates that coupling of the oxidation and reduction pathways in the mechanism creates several possibilities for unstable steady states and synergic oscillatory dynamics. One of them, for example, is based on an autocatalytic pathway, where the oxygen for catalytic burning is provided by nitrogen oxides rather than directly supplied.

The stoichiometric networks approach provides a natural way of decomposing the entire network into subsystems, which still may couple the oxidation and reduction pathways, and identify those that are potentially a source of nontrivial dynamical instabilities.

References

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