MAO- and Borate-Free Activating Supports for Group 4 Metallocene and Post-Metallocene Catalysts of α-Olefin Polymerization and Oligomerization

Abstract

Modern industry of advanced polyolefins extensively uses Group 4 metallocene and post-metallocene catalysts. High-throughput polyolefin technologies demand the use of heterogeneous catalysts with a given particle size and morphology, high thermal stability, and controlled productivity. Conventional Group 4 metal single-site heterogeneous catalysts require the use of high-cost methylalumoxane (MAO) or perfluoroaryl borate activators. However, a number of inorganic phases, containing highly acidic Lewis and Brønsted sites, are able to activate Group 4 metal pre-catalysts using low-cost and affordable alkylaluminums. In the present review, we gathered comprehensive information on MAO- and borate-free activating supports of different types and discussed the surface nature and chemistry of these phases, examples of their use in the polymerization of ethylene and α-olefins, and prospects of the further development for applications in the polyolefin industry.

Research Progress of Iron Catalysts with N,N,N‐tridentate Ligands for Ethylene Polymerization

“…Among the bis(arylimino)pyridine iron catalysts, the commonly used cocatalysts are MAO and MMAO, and there are some other cocatalysts ( iso ‐butylaluminoxane, ethylaluminoxane and alkylaluminum/urea hybrid) that are mainly used for ethylene oligomerization [32,69–76] . Organoboride cocatalysts show unsatisfactory results in stability and anion coordination capacity, and they are rarely used as activators of the bis(arylimino)pyridine iron catalyst [77–81] . MAO is typically produced via controlled hydrolysis of trimethylaluminum (TMA), leading to a rather complex mixture of species.…”

“…[32,[69][70][71][72][73][74][75][76] Organoboride cocatalysts show unsatisfactory results in stability and anion coordination capacity, and they are rarely used as activators of the bis(arylimino)pyridine iron catalyst. [77][78][79][80][81] MAO is typically produced via controlled hydrolysis of trimethylaluminum (TMA), leading to a rather complex mixture of species. Besides, some residual TMA from the MAO (typically accounting for up to 1/3 of the total Al content) reduces the catalyst activity.…”

Mechanistic Insights of Ethylene Polymerization on Phillips Chromium Catalysts

“…Cr/Al 2 O 3 catalysts have some drawbacks (e.g., lower fragility, porosity, and surface area, more rapid deactivation) in comparison with Cr/SiO 2 systems [ 3 , 4 ]. However, the recent progress in the development of Al 2 O 3 -based supports [ 119 , 120 ] does not exclude the possibility of further studies and applications of alumina as applied to PCCs. In 2018, Groppo and colleagues conducted a separate study of the nature and activity of Cr sites on an alumina surface [ 121 ].…”

“…The development of hybrid catalysts is a very attractive idea, but the compatibility of the desired components (R 3 Al and donors for Ziegler–Natta catalysts, MAO or R 3 Al/perfluoroaryl borates for single-site systems, no additives for PCCs) needs to be considered during the formulation process. Some of these additives are mutually incompatible, and it is hardly surprising that only Ziegler–Natta/metallocene hybrid catalysts have demonstrated real prospects to put into practice [ 124 , 125 ] with the use of “activating” supports [ 120 ].…”