Development and characterization of NOx-reductive catalytic coating systems for lean-burn engines

Abstract

In the present work Pd- and Rh- integrated perovskites are developed and characterized regarding the state of Pd and catalytic activity by means of microstructural and spectroscopic methods (XRD, SEM, TEM, XPS, and -SCR-NOx). Pd in the La-based perovskite partially displays a reversible diffusion mechanism under redox atmospheres at 600°C. These effects produce a self-regenerative mechanism at relatively high temperatures. Catalytic testing under model gas mixtures of powders and coatings of these perovskites proves the potential of these materials for effective NOx-reduction under lean conditions. Hydrogen provides the best NO-reduction results among the employed reducing agents (i.e. H2, C3H6, and C8H18). The Pd-integrated Perovskites display peak NO-conversions of 72 % and N2-selectivities of 72 % in the presence of H2O-vapour and CO2 at temperatures below 300°C. For instance, Ba- and Ce- substituted perovskites are also active for NO-reduction up to 400°C.