Toward an Understanding of the Molecular Level Properties of Ziegler−Natta Catalyst Support with and without the Internal Electron Donor

Abstract

Two Ziegler−Natta catalysts supported on molecularadducts, namely, MgCl2·6EtOH (ME) and MgCl2·5EtOH·EtOOCPh (Est-ME), have been prepared. A systematic effort has been made to unravel the molecular level structure−property relationships of the catalysts and adducts. Ethylbenzoate is an internal electron donor, and its in situ formation through EtOH + PhCOCl coupling is successfully achieved. The above adduct has been treated with TiCl4, and the resultant catalyst (Ti/Est-ME) is evaluated for ethylene polymerization activity. IR and 13C CP/MAS NMR of Est-ME (Ti/Est-ME) show carbonyl features at 1730 (1680) cm−1 and 169 (170) δ, respectively, providing direct support for the presence of ester as an integral part. In spite of low surface area, Ti/Est-ME gives higher yield for ethylene polymerization than the one derived from ME. The results indicate that electronic environment is more important than surface area or any other single factor in determining the polymerization activity.

Heterogeneous Ziegler–Natta catalysts with various sizes of MgCl2 crystallites: synthesis and characterization

“…The n-heptane solution remaining in the catalyst showed absorption between 2900 and 2967 cm −1 and two separate peaks at 1465 and 1380 cm −1 , which is in agreement with reports by Blitz et al, Deslauriers et al and Thushara et al [34,37,38].…”

Spectroscopic Investigation of Heterogeneous Ziegler–Natta Catalysts: Ti and Mg Chloride Tetrahydrofuranates, Their Interaction Compound, and the Role of the Activator

“…[8, 10,11] Nevertheless, to the best of our knowledge, there are very few examples of combination of both techniques to investigate Ziegler-Natta catalysts. [11] The complexes investigated in this work offered the possibility to compare the vibrational properties of the electron-donor molecule (thf) in interaction with both Ti IV and Ti III metal …”

“…[11] The complexes investigated in this work offered the possibility to compare the vibrational properties of the electron-donor molecule (thf) in interaction with both Ti IV and Ti III metal …”

“…Heterogeneous ZieglerNatta catalysts have the monopoly of the production of isotactic polypropylene, and they also show a fairly good ability to insert 1-alkenes inside growing polyethylene chains. [3] The great industrial impact of these catalysts explains the large amount of experimental [4][5][6][7][8][9][10][11] and theoretical [9,[12][13][14][15][16][17][18] efforts that have been devoted so far to the characterization of the active sites. However, despite the large number of scientific works, realistic models are still not yet fully assessed.…”

Effect of internal electron donor on the active center distribution in MgCl2-supported Ziegler–Natta catalyst

“…ID can bind strongly to MgCl 2 crystallites formed in the preparation process, thus stabilizing these crystallites. Consequently, the amount and distribution of TiCl 4 adsorbed on the MgCl 2 crystallites will also be affected by the ID [4]. Meanwhile, ID plays a vital role in controlling the catalyst stereoselectivity, leading to evident improvement in isotacticity of polyolefins [5].…”