Abstract
In this investigation different experimental methods to determine the platinum dispersion of Pt/BaO/Al 2O 3 NO x storage catalysts are compared. The dispersion of platinum is determined independently using temperature programmed desorption of CO, dissociation of N 2O, static volumetric CO and H 2 chemisorption, dynamic CO chemisorption and transmission electron microscopy. For Pt/BaO/Al 2O 3, reproducible results are obtained when the platinum dispersion is determined from N 2O dissociation, CO and H 2 chemisorption. However, repeated CO-TPD experiments result in decreased amount of desorbed CO, which limits this method to determine platinum dispersion for Pt/BaO/Al 2O 3 samples. For Pt/Al 2O 3, similar values for platinum dispersion are obtained for all methods used in the study. In addition to the platinum dispersion investigations, the surface morphology of Pt/BaO/Al 2O 3 samples and the distribution of different elements are studied using SEM-EDS. The SEM-EDS analyses show that the platinum is evenly distributed over the entire sample surface, while the distribution of barium is more uneven.
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