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 s mall- and wide-angle X-ray scattering in order to get information on the cr ystallites dimensions, structural disorder and surface areas. The results w ere correlated with catalytic activities in polymerization of propylene. It was shown that the structural variations, which mainly influence the catal ytic 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 s urface areas of the examined samples, determined by BET, are less meaningfu l than the data obtained by small-angle X-ray scattering, probably for the presence of intra-particle closed pores and/or microporosity. (C) 2000 Else vier Science Ltd. All rights reserved.