Despite 60 years of history and a stunning success, Ti-based Ziegler−Natta catalysts for the production of isotactic polypropylene remain black-box systems, and progress still relies on trial and error. This represents a limitation in a moment when the most widely used industrial systems, containing phthalates as selective modifiers, need to be replaced because of a recent REACH ban. In view of the great complexity of the chemical and physical variables and the heavy nonlinearity of their effects, a high-/ medium-throughput approach to this catalysis is highly desirable; herein we introduce an integrated medium-throughput workflow spanning from propene polymerization to polypropylene microstructural characterization and combining a 10 2 -fold throughput intensification with quality standards equal or higher than conventional methods.

Highly active molecular catalysts for olefin polymerization are extremely difficult to run in high-throughput experimentation (HTE) platforms. With common activators like methylaluminoxane (MAO) or a combination of tri-iso-butylaluminum and trityl tetrakis(perfluorophenyl)borate (TIBA/TTB), the necessary downscaling ends up with (sub)nanomole precatalyst loadings and poorly reproducible results due to the presence of adventitious impurities in similar amounts. Unexpectedly, we have now discovered that a convenient solution to this problem is provided by TIBA/AB (AB = N,N-dimethylanilinium tetrakis(perfluorophenyl)borate), a long-known but relatively uncommon protic activator. Indeed, with a proper operating protocol, a tunable precatalyst activation delay (minutes to hours) can be achieved, and even at high (≥10 nmol) catalyst loadings, a transient phase of well-controlled activity can be maintained long enough to produce the polymer amounts necessary for the characterizations under highly reproducible conditions. Importantly, polymer properties were not affected by choice of the activator, provided that the polymerization was kinetically controlled, which makes TIBA/AB the best option for HTE screenings of industrially relevant catalysts. Article pubs.acs.org/IECR

This paper introduces a high throughput experimentation method for fast and accurate evaluations of regioselectivity in Ziegler–Natta (ZN) propene polymerizations. With a simple protocol, the (very low) fraction of regio-irregular 2,1 monomeric units in the polymers can be quantitated by means of 13C NMR chain-end analyses on single H2-terminated polypropylene samples. The method, that was successfully validated for three representative ZN catalyst systems, also provides information on catalyst “dormancy” and propensity to undergo chain hydrogenolysis. This opens the door to the rapid and accurate implementation of quantitative structure–activity relationship (QSAR) databases of regioselectivity and “hydrogen response” in this important industrial catalysis.

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A class II hybrid sol-gel material was prepared starting from zirconium(IV) propoxide and 2,4-pentanedione and its catalytic activity in the removal of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) was revealed. The thermal and structural characterization, performed by thermogravimetry, differential thermal analysis, and diffuse reflectance Fourier transform infrared spectroscopy, demonstrated the hybrid nature of the material. The structure of the material can be described as a polymeric network of zirconium oxo clusters, on the surface of which large part of Zr(4+) ions are involved in strong complexation equilibria with acetylacetonate (acac) ligands. The incubation of MCPA in the presence of this material yielded an herbicide removal fraction up to 98%. A two-step mechanism was proposed for the MCPA removal, in which a reversible first-order adsorption of the herbicide is followed by its catalytic degradation. The nature of the products of the MCPA catalytic degradation as well as the reaction conditions adopted do not support typical oxidation pathways involving radicals, suggesting the existence of a different mechanism in which the Zr(4+):acac enol-type complex can act as Lewis acid catalyst.