Impact of the method of Mg2+ cation introducing into the titanium post-metallocene catalytic system on their activity

This work shows for the first time the influence of the method of introducing Mg compounds into a post-metallocene-type catalytic system on its catalytical performance and the properties of the resulting polymer, and it is concluded that the real catalytic center is heterometallic Ti/Mg complexes. Three different approaches were compared to introducing Mg compounds into catalytic systems containing a titanium(IV) dichloride complex with an (O^O)2− type ligand and an organoaluminium compound—the use of Al/Mg co-catalysts, the immobilization of a Ti complex on the surface of anhydrous MgCl2 and in situ preparation of heterometallic Ti/Mg complexes. All three approaches lead to the production of ultra-high molecular weight polyethylene, but systems with externally introduced magnesium chloride showed the lowest productivity. On the contrary, heterometallic Ti/Mg precatalysts are successfully activated by conventional organoaluminium compounds (Et3Al, iBu3Al, MAO) and are superior to the reference catalytic system both in activity and in polymer molecular weights. Their use makes it possible to reduce the Ti/Mg molar ratio in catalytic systems from 1:300 to 1:1–2. The resulting UHMWPE samples are suitable for solvent-free solid-phase processing into high-strength, high-modulus film threads. © 2025 Elsevier B.V., All rights reserved.