The impact of CO and C 3 H 6 pulses on PtO x reduction and NO oxidation in a diesel oxidation catalyst

Abstract A reversible deactivation of a diesel oxidation catalyst (DOC) due to the platinum oxide (PtO x ) formation is observed under lean conditions. Among others, the gradual build-up of PtO x leads to a decreasing activity for NO oxidation. It is known that PtO x formation is caused by O 2 and NO 2 present in the gas mixture and that platinum oxide can be reduced by NO at lower temperatures or thermally decomposed at high temperatures. In this paper we present experimental and modeling results showing that PtO x can be reduced also by CO and C 3 H 6 pulses. First, temperature ramps from 120 to 420 °C and back to 120 °C were performed with a constant inlet gas composition starting with a reduced catalyst. A higher NO oxidation activity was observed during the heat-up phase than during the subsequent cool-down phase, indicating formation of PtO x . The catalytic activity during the cool-down ramp was partially restored by pulses with an increased CO and C 3 H 6 concentration (while still keeping lean conditions). The maximum effect of pulses was observed around the light-off temperature for CO and C 3 H 6 oxidation. A global kinetic model was developed, considering PtO x existence and its reduction by CO and C 3 H 6 pulses. The model was further validated by isothermal experiments, showing gradual decrease of NO oxidation activity and its recovery by CO and C 3 H 6 at several different temperatures.