Effects of catalyst aging on the activity and selectivity of commercial three-way catalysts

Abstract

A Pd catalyst is particularly effective for the oxidation of CO and C3H6 at low temperatures, while the Pt/Rh/Ce catalyst is active for NO reduction. The TWC activity of both catalysts generally decreased as the catalyst mileage increased. However, the NO reduction activity was less affected by catalyst aging compared to the oxidation reactions. The selectivity of the catalysts in favor of the CO-O-2 reaction (vs. C3H6-O-2 reaction) in the O-2 partitioning experiments became less pronounced as the catalyst aged. The NO partitioning experiments reveal the superior capability of H-2 in NO reduction to the other reductants (CO and C3H6) examined in the present study. The reactivities of NO with both H-2 and CO were found to decrease upon catalyst aging, resulting in decreased overall NO removal activity.