Activity Function for Describing Alteration of Three-Way Catalyst Performance over Palladium-Only Three-Way Catalysts by Catalyst Mileage

A simple three-way catalyst (TWC) activity function based upon the alteration of the Pd metallic surface area (MSA) of Pd-only commercial monolith TWCs has been developed to describe the change of the catalytic performance with respect to the Pd metal loading varying from 5 to 10 g/L and the field-aged catalyst mileage from 4K (stabilized) to 98K miles. Particularly, the change of the Pd MSA of TWC with respect to the catalyst mileage has been well-correlated by the second-order sintering kinetics, regardless of the Pd content of the TWC. The TWC activity function was incorporated into the primary reaction kinetics developed for the stabilized 4K Pd-only TWCs to predict the deactivation of the Pd-only TWC performance with respect to the field-aged mileage. The overall reaction kinetic model with the TWC activity function developed in the present study is capable of describing the alteration of TWC performance with respect to the catalyst mileage, regardless of the catalyst metal content.