Isotopic study of the influence of oxygen interaction and surface species over different catalysts on the soot removal mechanism.

In order to improve the catalytic formulations for soot removal in after-treatment emission control technologies for gasoline and diesel engine vehicle, an isotopic study was approached using transitory labeled oxygen response method over model catalysts that allows the unraveling of soot oxidation mechanism. Ce-based materials promote oxygen exchange associated with the high population of lattice oxygen species (O2-) denoted as O I type. The incorporation of praseodymium produces a Pr3+ enrichment that decrease the energy for oxygen release and increase oxygen mobility through surface and subsurface oxygen centers (O II type) depending on the synthesis procedure. For PtBaK catalyst, O III species are responsible for oxygen exchange. Gas-solid reaction between soot and gas phase molecular oxygen is responsible for direct uncatalyzed soot oxidation. For ceria containing catalysts, low-temperature soot removal takes place through the intervention of lattice atomic species and superoxide species. For DPNR model catalyst, PtBaK/Al 2 O 3 , the soot elimination occurs with the intervention of O III type centers. In the presence NO, the assisted and cooperative mechanism due to NO 2 and the intervention of the adsorbed nitrate species on the trimetallic catalyst enhances soot removal capacity. [Display omitted] • For CeO 2 catalysts the 18O 2 /16O 2 exchange prevails and Pr increases oxygen uptake. • PtBaK promotes single-atom exchange being 18O16O the main detected species. • Soot removal mechanism depends on oxygen species (O I , O II or O III type) mobility. • CePr mixed oxides are able to remove soot at low temperature under inert conditions. • DPNR catalyst is more efficient in the presence of NO due to nitrate intervention. [ABSTRACT FROM AUTHOR]