MnOx-CeO2 mixed oxides as the catalyst for NO-assisted soot oxidation: The key role of NO adsorption/desorption on catalytic activity

The role of NO adsorption/desorption on soot oxidation activity of MnOx-CeO2 mixed oxides was investigated in this work. NO adsorption/desorption on MnOx-CeO2 results in a visible promotion of the low-temperature reactivity. Physico-chemical characterization reveals that the formation of NO adsorbed species, mainly nitrates, leads to changes in the surface Ce/Mn states and in an increase of oxygen vacancies. Moreover, TPD-MS indicates that the decomposition of surface nitrates accelerates the desorption of oxygen in the catalyst. Soot-TPR-MS confirms that the oxygen species desorbed from nitrates decomposition play an important role during soot oxidation. The isothermal experiments evidence that NO adsorption/desorption enhances soot oxidation rate, with active oxygen playing a key role in a cooperative C + NO2 + O-2 reaction with the catalyst.