Assessing the effect of O2 dithering on CH4 oxidation on Pd/Al2O3

Under periodic lean/rich operation generated by repeated O2 pulses (O2-dithering), the abatement of CH4 and NO is enhanced compared to static operation. However, it is not well understood how the dithering parameters (pulse amplitude and frequency) affect CH4 conversion, making it difficult to anticipate the impact of such pulses on the catalytic performance. Here, we show that the effect of O2-dithering on the activity of Pd/Al2O3 can be reliably assessed as a function of dithering parameters, temperature, and exhaust gas composition. Operando Xray absorption spectroscopy was used to support the conclusions based on considerations of the Pd oxidation state. Our work relies on explicit calculations of the O2 concentration present in the reactive feed, which is based on the amount of O2 pulsed to the system and the pollutants' conversion. Since NO contributes to the amount of oxygen available during reaction, its concentration and conversion need to be correctly evaluated.