A research project has been undertaken with the aim of characterizing and modeling the oxygen storage process in a three way automotive catalyst. The model consists of an oxygen storage sub-model and a kinetic reaction sub-model. Validation data for these models was recorded from a purpose-built catalyst flow reactor which uses O2 and NO as the oxidizing agents and CO, C3H6 and C3H8 as the reducing agents.
The main focus of the work is the oxygen storage sub-model and the identification of the relevant constants for the reaction kinetic equations. The procedure used for measuring the oxygen storage capacity, and the oxygen storage and release rates from ceria (CeO2), is presented and discussed. The activation energies and activity factors for all the oxidation and reduction components were also found from the apparatus and used in the model.
The results show that, with the exception of the oxidation constant for O2, which is due, in part, to the interaction between ceria and platinum, the oxidation and reduction rate constants increase with increasing temperature. The relationship between ceria and platinum was investigated further by performing a second series of tests in the absence of platinum by using ceria powder. Finally, a validation procedure was performed which showed good correlation between the measured and predicted oxygen storage capacity.