BIMODAL PARTICLE-SIZE DISTRIBUTION AND SURFACE SEGREGATION OF ZEOLITE-SUPPORTED CATALYSTS FROM XPS DATA

This paper deals with the quantitation of XPS data of supported catalysts using the so-called sheet stacking model with surface segregation. The supported material was assumed to have a bimodal distribution with a fraction x1 of small particles (size C1) homogeneously distributed throughout the support and a fraction of larger particles (size C2) segregated on the external surface of the support. Based on an arbitrary value of C1, the method proposed provides estimates for C2 and the relative amount of each fraction of particles. Effects of various parameters on the particle distribution (C2 and x1) were assessed.The merits and limitations of the proposed method are discussed.