NOx Adsorption Study over Pt-Ba/Alumina Catalysts by FT-IR and Pulse Experiments

Adsorption of NO, NO/O2, and NO2 on Pt–Ba–Al–O system is investigated at 350 °C by the transient response method (TRM) and FT-IR spectroscopy. The data suggest that in the presence of oxygen, NO is effectively adsorbed (at a Ba site in proximity of a Pt site) through stepwise oxidation to form at first nitrites that are progressively transformed into nitrates. NO is also oxidized to NO2 over Pt in the presence of oxygen. NO2 is directly adsorbed to form Ba nitrates according to a disproportionation reaction, which occurs with the evolution of NO. The stepwise oxidation route seems to play a major role in NOx storage from NO/O2 mixtures.