Pt–Ba–Al2O3 for NOx storage and reduction: Characterization of the dispersed species

Pt–Ba–Al2O3 active and selective for NOx storage and selective reduction to N2 has been prepared and tested. Characterization of the parent Al2O3, Pt–Al2O3 and Ba–Al2O3 materials, as well as of Pt–Ba–Al2O3 catalyst in the oxidized, reduced and sulphated state has been performed by FT-IR spectroscopy of low-temperature adsorbed carbon monoxide and of adsorbed acetonitrile. XRD, TEM and XPS analyses have also been performed. Evidence for the predominance of Ba species, which are highly dispersed on the alumina support surface, and may be carbonated or sulphated, has been provided. Competitive interaction of Pt and Ba species with the surface sites of alumina has also been found.