Formation of Highly Stereospecific Ziegler–Natta Catalysts in the Presence of Phthalates Studied by Nonempirical Structure Determination

Internal donors (IDs) are essential components of highly performant heterogeneous Ziegler–Natta catalysts that are directly connected to the creation of stereospecific active sites. Although this connection is still not fully understood, theoretical investigations have played an important role in understanding how IDs can increase the stereospecificity by adsorbing next to TiCl4. In this study, we performed a nonempirical structure determination, combining density functional theory and a genetic algorithm, of nanoplates with varying ID/Ti ratio and coverage: 19MgCl2/5DEP, 19MgCl2/2TiCl4/5DEP, and 19MgCl2/4TiCl4/2DEP. Their morphology and active site precursor, TiCl4, were investigated with the objective of understanding if the adsorbate-induced support reconstruction can ensure that IDs become stereocontrolling ligands and validating our previous findings about the ID-driven improvements to the catalyst. We conclude that the exposure of short {110} terraces terminated by sharp edges is the main morphological motif ensuring that IDs adsorb close to TiCl4, becoming stereocontrolling ligands and that their appearance is dependent on high ID/Ti ratio and coverage. In addition, we discuss the individual impact of DEP and TiCl4 gradual mixing on the nanoplates and determine the composition most capable of explaining the known polymerization performance of phthalate-containing Ziegler–Natta catalysts.