Determination of the Metal Dispersion of Supported Catalysts Using XPS

Abstract

In this work, recent applications of XPS for the dispersion measurements of oxidic supports and metal catalysts were discussed.The most frequently used models, those of Kerkhof?Moulijn and Davis, were selected to give an overview of severalapplications in the study of catalysts, based on noble (Pd, Au, Ag, and Rh) and non-noble metals (Co, Ni). In the case of thedispersion of different promoters on the surface of oxidic supports, the Kerkhof?Moulijn model was often applied. Goodcorrelations were achieved for high surface area Al2O3supports modified by La, B and W. This model was also applied toanalyze the dispersion of Co, Ni, Pd and Rh on oxidic supports, making it possible to propose the limit of monolayer formationfor homogeneously distributed metal particles. The Davis model was developed for the estimation of metal particlesizes. This method considered the morphology of the metal particles and assumed a diamond-shaped support. The XPSresults combined with the information obtained through other techniques showed the potential application of this model inthe determination of metal particle sizes for Rh, Au, Pd and Ni based catalysts.