Polyethylenimines: Multidentate Electron Donors for Ziegler–Natta Catalysts

Abstract

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 MgCl 2 support was studied using computational (DFT; M06-2X) and experimental (PXRD, DRIFT, CP/MAS 13 C NMR) methods. Quantum chemical calculations suggest that the structural variations in PEIs significantly affect their ability to stabilize the catalytically relevant MgCl 2 surfaces. Coordination on the (104) surface seems to be favored upon consideration of the layered structure of MgCl 2 . 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 MgCl 2 . Based on spectroscopic data, nitrogen atoms of primary, secondary, and tertiary amino groups can participate in coordination to MgCl 2 . 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 (MgCl 2 /PEI/TiCl 4 ) 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 MgCl 2 support and indicate their potential as a new type of internal electron donors for Ziegler−Natta catalysts.

Adsorption of Titanium Tetrachloride on Magnesium Dichloride Clusters

“…All structures were fully optimized by the M06-2X metahybrid GGA functional of the Minnesota 06 series, in combination with TZVP basis set by Ahlrichs and coworkers . The M06 functionals have turned out as the method of choice for systems involving dispersive interactions arising from metals bridged by halide and alkyl groups, ,− and we have previously used the method for describing MgCl 2 - and TiCl 4 -containing systems analogous to the systems reported here. ,, Vibrational frequencies were calculated by the harmonic approximation to verify the structures as true minima in the potential energy surface and to obtain Gibbs energies, which were calculated at T = 298 K and p = 1 atm. Condensed phase Gibbs energies were estimated from the reported gas-phase calculations by multiplication of the T Δ S term of G = H – T Δ S by 2/3 as suggested and employed in the previous literature. − All calculations were carried out by Gaussian 09 …”

Role of a Multidentate Carbonate Donor in MgCl2-Supported Ziegler–Natta Olefin Polymerization Catalysis: An Experimental and Computational Approach

“…Currently, Z–N researchers are focusing on designing new donor catalyst systems, particularly multidentate donor catalyst systems. Recently, Pakkanen and co-workers have employed nitrogen-containing polyethylenimines as multidentate donors and observed an effective donor catalyst system for Z–N olefin polymerization. However, to the best of our knowledge, there are no experimental and computational studies on multidentate carbonate donors for Z–N olefin polymerization.…”

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

“…[1] Since its discovery in the 1950s by Karl Ziegler and Giulio Natta, for which they received the Nobel prize in 1963, [2,3] continuous efforts to improve the performance of the ZN systems, concerning their activity and the selectivity, have been undertaken, along with understanding at the molecular level, by employing various experimental [4][5][6][7][8][9][10][11] and computational tools. The main components of the ZN system are (i) MgCl 2 as a catalyst support, (ii) TiCl 4 as precatalyst, (iii) triethylaluminum (teal) as an alkylating agent, and (iv) Lewis base donors (e. g. oxygen-containing molecules and nitrogen-containing polymers [35] ). Donors are generally classified into (i) internal donors (D I ) that are added during the catalyst preparation, such as ethyl benzoate, [26,[36][37][38][39][40][41] diethers, [13,27,38,[42][43][44] phthalates, [13,22,38,45,46] tetrahydrofuran, [29,47] and succinates, [27,38,48] and (ii) external donors (D E ) that are added along with the alkylating agent, such as alkoxysilanes [38,46,49] and p-ethoxyethylbenzoate.…”

“…The main components of the ZN system are (i) MgCl2 as a catalyst support, (ii) TiCl4 as precatalyst, (iii) triethylaluminum (teal) as an alkylating agent, and (iv) Lewis base donors (e.g. oxygen-containing molecules and nitrogen-containing polymers [35] ). Donors are generally classified into (i) internal donors (DI) that are added during the catalyst preparation, such as ethyl benzoate, [26,[36][37][38][39][40][41] diethers, [13,27,38,[42][43][44] phthalates, [13,22,38,45,46] tetrahydrofuran, [29,47] and succinates, [27,38,48] and (ii) external donors (DE) that are added along with the alkylating agent, such as alkoxysilanes [38,46,49] and p-ethoxyethylbenzoate.…”