Small- and wide-angle X-ray scattering analysis of Ziegler–Natta catalysts: structural disorder, surface area and activity

An analysis was carried out of some Ziegler–Natta catalysts precursors by small- and wide-angle X-ray scattering in order to get information on the crystallites dimensions, structural disorder and surface areas. The results were correlated with catalytic activities in polymerization of propylene. It was shown that the structural variations, which mainly influence the catalytic activity, are associated with the rotational disorder of the Cl–Mg–Cl triple layers and that the crystallites dimensions and surface areas play a determinant role in the same activity. Furthermore it was shown that the surface areas of the examined samples, determined by BET, are less meaningful than the data obtained by small-angle X-ray scattering, probably for the presence of intra-particle closed pores and/or microporosity.