Exploring microstructure of MgCl2·nEtOH adducts for Ziegler-Natta catalysts

Abstract

The activation of MgCl2 through the formation of MgCl2·nEtOH adducts is considered the principal step for the preparation of high performance Ziegler-Natta catalysts for olefins polymerizations in industry. Despite this importance, due to the complicated microstructure of the adducts, the precise structural characterization of these compounds has been left behind. In this research, four MgCl2.nEtOH adducts (with n = 0.6, 1.0, 1.8, and 3.2) were prepared by melt quenching procedure and assessed thoroughly by different techniques. Despite the multiple peaks in TGA analysis, similar FTIR spectra were recorded, and the adducts with n = 3.2 revealed sticky nature in SEM pictures which enhanced their particle size and broadened SPAN. According to the XRD spectra, the adducts showed distinct peaks related to the lateral cuts of distorted MgCl2, in which the ratio of α-MgCl2 to β-MgCl2 form enhanced by increasing the EtOH content, that was further confirmed by DFT calculations, even though it must be accepted that it is only a minimalist exercise in terms of a clear characterization of the adducts.