Heterogeneous Copolymerization of Ethylene and α‐olefins Using Aluminohydride‐Zirconocene/SiO2/MAO by High‐Throughput Screening

Copolymerizations of ethylene and α-olefins (1-hexene and 1-octene) using a supported catalyst derived from the activation of a zirconocene aluminohydride complex with PMAO and MMAO are reported. The supported (nBu-Cp 2 ZrH 3 AlH 2 )/SiO 2 / MAO system was evaluated by high-throughput techniques, in order to find approaches to the optimal copolymerization conditions. The polymerization reactions were carried out in a parallel polymerization reactors system (PPR) by Symyx Technologies, Inc. The screening of the activity of the supported system and the molecular weight (MW) of the polymers and copolymers obtained in the PPR, allowed us to optimize copolymerization conditions, like hydrogen (H 2 ) addition to control MW and molecular weight distribution (MWD), polymerization temperature, cocatalyst ratio, and solvent type. The copolymerization reactions were scaled-up in order to validate the performance of the catalytic system at higher polymerization scales, according to the results obtained in the combinatorial phase. The scaled-up copolymerizations of ethylene with 1-hexene and 1-octene, showed high activities and MW, and low comonomer incorporation (from 0.3 to 1.3 mol-%, determined by 13 C NMR). However, the crystallinity (X c ), thermal properties (T c and T m ) and densities of the polyethylenes obtained with the supported (nBu-Cp 2 ZrH 3 AlH 2 )/SiO 2 /MAO system, were significantly modified, approaching those of metallocene linear low-density polyethylenes (mLLDPE).