5 years ago

Polyethylenimines: Multidentate Electron Donors for Ziegler–Natta Catalysts

Polyethylenimines: Multidentate Electron Donors for Ziegler–Natta Catalysts
Kumudini Jayaratne, Peter Denifl, Tuula T. Pakkanen, Andrey S. Bazhenov, Ville H. Nissinen, Timo Leinonen, Tapani A. Pakkanen, Anneli Pakkanen, Mikko Linnolahti
Polyethylenimines, polymers bearing amino functionalities, are studied for the first time as internal electron donors for Ziegler–Natta catalysts. An advantage of polyethylenimines (PEIs) compared to the conventional phthalate electron donors is their relative harmlessness. Interaction of PEI with MgCl2 support was studied using computational (DFT; M06-2X) and experimental (PXRD, DRIFT, CP/MAS 13C NMR) methods. Quantum chemical calculations suggest that the structural variations in PEIs significantly affect their ability to stabilize the catalytically relevant MgCl2 surfaces. Coordination on the (104) surface seems to be favored upon consideration of the layered structure of MgCl2. The surface stabilization energies of branched PEIs are of the same magnitude with a phthalate electron donor reference. Experimental results indicate, in agreement with theoretical results, a strong coordination ability of branched PEI through nitrogen atoms to MgCl2. Based on spectroscopic data, nitrogen atoms of primary, secondary, and tertiary amino groups can participate in coordination to MgCl2. Calculations indicate that the strongest coordination of branched PEI occurs through primary amino groups. A Ziegler–Natta catalyst containing branched PEI as an internal electron donor (MgCl2/PEI/TiCl4) showed a reasonably high activity in ethylene/1-butene copolymerization. Overall, the combined computational and experimental results provide detailed information about coordination of nitrogen-containing polymeric electron donors to MgCl2 support and indicate their potential as a new type of internal electron donors for Ziegler–Natta catalysts.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b05343

DOI: 10.1021/acs.jpcc.7b05343

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