Control of Ziegler-Natta catalyst activity by structural design of external donor

Vikasa, Gurmeet Singhb, Hemant K. Kashyapa

aDepartment of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India

bPetrochemical & Polymer Department, R&D Center, IndianOil Corporation Ltd., Sector-13, Faridabad 121007, Haryana, India

The laboratory synthesized two new cycloalkoxysilanes have been evaluated as external donors used in heterogeneous Ziegler-Natta catalyst for synthesis of polypropylene. Polymerization of propylene was carried out using 4th generation Ziegler-Natta (ZN) catalyst containing diisobutylphthalate (DIBP) as an internal donor in conjunction with triethylaluminium (TEAL) as cocatalyst. To exploit the experimental behavior and structural aspects of these new external donors i.e. control of the tacticity and productivity of polypropylene polymer, quantum mechanical calculations (DFT) using B3LYP (Becke-3-parameters,Lee-Yang-Parr) functional were performed on known commercial alkoxysilanes to generate the electronic and structural aspects of external donors then these were implemented over newly synthesized external donors. The theoretical binding energies of complex formed between the external donors and the co- catalyst were found to have a fair correlation with the experimentally measured productivity of polypropylene. The comparative results confirmed that certain essential structural characteristics are required to achieve a high activity of catalyst and stereospecificity of polypropylene.

 

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