Insights into the Nature of Self‐Extinguishing External Donors for Ziegler‐Natta Catalysis: A Combined Experimental and DFT Study

Abstract

Developing donors for Ziegler‐Natta (ZN) catalysis to control the polymerization reaction and produce polymers with desirable properties has always been challenging due to the multi‐component nature of the catalytic systems. Here, we have developed a new synthetic protocol for making two external donors, D1 (2,2,2‐trifluoroethyl myristate) and D2 (2,2,2‐trifluoroethyl palmitate) that show self‐extinguishing properties, followed by a systematic DFT study to understand this peculiar property of these donors. D1 and D2 can undergo parallel reactions with aluminum and titanium species present in the system to produce ketones and aldehydes, which are poisons for ZN catalytic systems, thus explaining their self‐extinguishing nature. The non‐covalent interaction between the long alkyl chain of the donors with the surface plays a vital role in determining the donors′ self‐extinguishing nature. There is a significant thermodynamic preference for the binding of the donor with the longer alkyl chain at the titanium center. The current work, therefore, provides interesting insights into how self‐extinguishing donors function in ZN catalytic systems.

Performance of post phthalate Ziegler Natta catalysts with activity limiting agents for propylene gas phase polymerization

“…The polymers in this study were characterized for molecular weight using GPC, stereoregularity using 13 C NMR, bulk density using a standard volume recipient, and particle size distribution using a Malvern Mastersizer 3000 particle analyzer. All the characterization methods have been described in a previous publication [15] .…”

“…However, for more detailed and accurate quantification of the stereo-errors in the polymer, 13 C NMR is used which we have utilized in this study. The assignment of the pentads was performed as described elsewhere [20] .…”

“…The polymers in this study were characterized as follows: using GPC for molecular weight, using 13 C NMR for stereoregularity, using a standard volume recipient for bulk density, and using a Malvern Mastersizer 3000 particle analyzer for particle size distribution. All the characterization methods were described in a previous publication.…”

“…One of the important properties of polypropylene is the stereoregularity of the polymer, which is measured using various characterization techniques; most notably for quick indication of tacticity, xylene soluble (XS) measurements are usually performed in industrial plants. However, for more detailed and accurate quantification of stereo-errors in the polymer, 13 C NMR is used which we utilized in this study. The assignment of the pentads was performed as described elsewhere.…”

Understanding the Role of Sulfonyl Amine Donors in Propylene Polymerization Using MgCl2-Supported Ziegler–Natta Catalyst

“…More importantly, the suitable internal donor and external donor pair can enhance the stereoregularity of the polymer product. The internal donor is typically added during the catalyst preparation, e.g., ethyl benzoate (EB) (third generation), dialkyl phthalate (fourth generation), 1,3-diether (fifth generation), and dialkyl succinate (sixth generation). − The external donor is added during the olefin polymerization process in combination with the cocatalyst AlR 3 , e.g., silane, and alkoxysilane. − The appropriate internal donor and external donor pair can control the regularity of the polypropylene and greatly increase the yield of the isotactic polypropylene. , In addition, the alkylation product AlR n Cl 3– n generated from AlR 3 could also be stably coordinated in the vicinity of the Ti active site, promoting the stereo- and regioselectivity of propylene insertion. , …”