Platinum dispersion measurements for Pt/BaO/Al2O3, NOx storage catalysts

In this investigation different experimental methods to determine the platinum dispersion of Pt/BaO/Al2O3 NOx storage catalysts are compared. The dispersion of platinum is determined independently using temperature programmed desorption of CO, dissociation of N2O, static volumetric CO and H-2 chemisorption, dynamic CO chemisorption and transmission electron microscopy. For Pt/BaO/Al2O3, reproducible results are obtained when the platinum dispersion is determined from N2O 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/Al2O3 samples. For Pt/Al2O3, 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/Ba/Al2O3 samples and the distribution of different elements are studied using SEWEDS. The SEM-EDS analyses show that the platinum is evenly distributed over the entire sample surface, while the distribution of barium is more uneven. (c) 2005 Elsevier B.V. All rights reserved.