Nucleation kinetics of MgCl2-ethanol adduct for the supported Ziegler-Natta catalysts with a thermodynamic approach

MgCl2-ethanol adducts play a key role in the synthesis of supported Ziegler-Natta catalysts. The morphology of the MgCl2-ethanol adducts, which is controlled by their crystallization process, can determine the structure and thus the property of the polyolefin products. Here we study the nucleation kinetics of MgCl2-ethanol adducts by measuring the metastable zone width (MSZW) and induction time at different temperatures. Supersaturation ratios used in induction time measurements were predicted by the Mixed Solvent Electrolyte (MSE) model embedded in OLI System. Nývlt′s approach was applied to determine MSZW. By the induction time measurement, the effect of temperature, and supersaturation were studied. It was found that induction time decreases as either temperature or supersaturation increases. The measured MSZW and induction time are used to estimate the nucleation kinetics of the system, and thereby distinguishing between the homogeneous and heterogeneous mechanisms. The interfacial tension and other related nucleation parameters were calculated from the induction time data. XRD and TGA indicate that the MgCl2-ethanol adduct has the stoichiometry of MgCl2·6C2H5OH.