Pt-Ba/MeO (where MeO=Al2O3, CeO2, SiO2 and ZrO2) NO x storage-reduction catalysts with Ba-loading varying from 0wt.% to 28wt.% were investigated concerning stability of Ba phases and NO x storage-reduction efficiency. For Pt-Ba/Al2O3 three different Ba-containing phases with different thermal stability are distinguished based on their interaction with the support. The relative concentration of these phases varies with the Ba-loading and NO x storage tests indicated that the BaCO3 phase decomposing between 400°C and 800°C (LT-BaCO3) is the most efficient Ba containing phase for NO x storage. Similar investigations of Pt-Ba catalysts supported on CeO2, SiO2 and ZrO2 showed that the relative amount of LT-BaCO3 phase depends also on the support material. NO x storage measurements confirmed a correlation between the concentration of LT-BaCO3 and NO x storage efficiency. Basicity and textural properties of the support are identified as crucial parameters for efficient NO x storage catalyst
