Theoretical study of heterogeneous Ziegler-Natta catalysts: A comparison between TiCl3 catalysts and MgCl2 supported catalysts by using paired interacting orbitals (PIO) analysis

Abstract

Two types of industrial heterogeneous Ziegler-Natta propylene polymerization catalysts, TiCl 3 type and MgCl 2 supported TiCl 4 type, were examined by paired interacting orbitals (PIO) analysis proposed by Fujimoto et al.. The ligand located trans to propylene was found to obstruct the insertion but was essential for the stereospecific insertion of propylene. The ligand located trans to the alkyl group of the active site was found to be necessary for activating the alkyl-Ti bond. The regioselectivity and stereoselectivity of the iso-specific polymerization site on the heterogeneous Ziegler-Natta catalyst system were confirmed. The polymerization activity of MgCl 2 supported TiCl 4 catalyst was larger than that of the TiCl 3 catalyst.

The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability

“…The development of such catalysts is a challenge to the polymer industry. To meet this challenge, clarification of the relationship between the structure of the active site and the catalyst performance on the basis of a precise and quantitative understanding of the polymerization mechanism of the catalyst α-TiCl 3 /Al(C 2 H 5 ) 3 is reported by Shiga [ 19 ].…”

“…According to Shiga, the crystal structure of TiCl 3 plays an important role in stereospecific polymerization of propylene [ 19 ]. Four crystalline modifications of TiCl 3 have been reported [ 116 ]: α-, γ-, δ-forms (violet), and the β-form (brown).…”

“…Since they constitute a considerable percentage of domestic garbage, polyolefins tend to fill up landfill sites by a significant amount. Therefore, some research activities are focusing on sustainable polyolefin production that can save on energy and raw material consumption for future generations [ 19 , 20 , 21 ].…”

Donor Decomposition by Lewis Acids in Ziegler–Natta Catalyst Systems: A Computational Investigation

“…This short (110) lateral cut has 150° bond angles with the (104) cuts and serves as the site for the binding of the titanium species. The site for the binding of the titanium at the (110) lateral cut is the Corradini site, originally proposed by Corradini and co-workers. , It should be noted that there are several other models that have been employed to mimic the MgCl 2 surface. − The currently adopted Cavallo model is similar to these models in that it also involves the binding of the titanium center to the (110) surface, though there is a significant difference in that the current work focuses on the binding of the donor to the titanium metal center, whereas previous studies have considered donor coordination to the (110) lateral cuts on a MgCl 2 support. ,, Furthermore, this model also has the advantage of having features that compare favorably to experimentally observed MgCl 2 surfaces, as discussed in the work of Cavallo and co-workers …”

The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

“…Although models for the support have been proposed in the past, [7,[26][27][28] a new model proposed by Cavallo and co-workers holds special promise. [8] This is because their model is based on a careful understanding of the conclusions of experimental and computational investigations.…”