Modeling periodic NOxNOx storage–reduction in the presence of CO2

The influence of temperature on periodic NOxNOx storage–reduction in the presence of CO2 has been investigated. A dynamic plug flow model and experiments performed in a packed bed reactor with a Pt–Ba/γγ-Al2O3 powder catalyst (1 wt% Pt and 30 wt% Ba) with different lean/rich cycle timings at different temperatures are compared. The model is based on a multiple storage site mechanism. The rate of NOxNOx storage increases with temperature. NOxNOx storage below 300 °C mainly occurs through NO adsorption as nitrites. The oxidation of nitrites to nitrates by NO2, with release of NO, is the predominant storage step, and its rate increases with temperature. The number of sites taking part in NOxNOx storage is independent of temperature and cycle time. The reduction of stored NOxNOx with H2H2 is efficient. However, with an increase in temperature, thermal decomposition of nitrites/nitrates results in a decrease of NOxNOx reduction.