A Quasi-steady-state analysis of the dynamics of two-species heterogeneous catalytic reactions

This study demonstrates how low-order algebraic non-linearities that exist in a simple two-component Langmuir-Hinshelwood type reaction kinetics (CO oxidation) are sufficient to produce rate multiplicities and oscillatory steady states (periodic solutions). A singular perturbation analysis is employed wherein certain quasi-steady-state considerations are made which lead to the definition of system manifolds and invariants along which the large-time dynamics of the system can be discerned without recourse to numerical integration. New results, confirmed by simulation, include an explanation for such experimentally observed pathological phenomena as the coexistence of oscillatory and stationary steady states and multi-peak oscillations. It is shown how the existence of oscillatory states and a plausible “buffering” physisorption surface reaction mechanism causing a periodic switching between these states and coexisting stationary ones can give rise to these multi-peak oscillations.