Naphthyridine Cyclopentadienyl Chromium Complexes as Single-Site Catalysts for the Formation of Ultrahigh Molecular Weight Polyethylene

Abstract

Cyclopentadienyl ligands functionalized with a 1,5-naphthyridine donor have been used for the formation of chromium(III) half-sandwich complexes. In addition to standard analytical characterization, the complexes have been investigated by paramagnetic 1H NMR spectroscopy combined with DFT calculations. After activation, highly active single-site catalysts are obtained that lead to the formation of ultrahigh molecular weight polyethylene (UHMW-PE). Evaluation of polymer formation after different polymerization times at low temperature shows that the number of active centers is low at the beginning, but increases with polymerization time.

Mathematical modeling of ethylene polymerization over advanced multisite catalysts: an artificial intelligence approach

“…The CrQCP pre-catalyst is a half-sandwich ( Fig. 4) chromium-based catalyst with chelating N-donor cyclopentadienyl ligand which makes it a superior catalyst to produce ultrahigh molecular weight polyethylene [64]. Generally, the average molecular weight of the resulting PE based of this precatalyst lies in the range 2 × 10 5 − 10 6 g/mol for homogeneous polymerization, whereas higher molecular weight ranges are achieved when the pre-catalyst is immobilized on a solid support or when a modifier is used [65].…”

Remarkable Promotion Effect of Sulfation over the SiO2‐Supported Vanadium‐Oxide‐Based Catalysts for UHMWPE

“…Under the same polymerization conditions, the sulfated catalysts show activity about twice as high as that of the ones modified by metal oxide only, and even four times higher than that of the SiO 2 supported one. [22] The characterization results of NH 3 -TPD indicate that the acidity of the catalysts is improved largely after sulfation, while the results of pyridine-adsorption-FTIR imply that a large amount of Lewis acid sites and a small amount of Brønsted acid sites are available on the surface of the catalysts. The enhanced acidity is likely derived from the superacidic metal oxide, which is strongly induced by the bonded SO and shows high electron deficiency.…”

“…In recent years, the versatile single‐site catalysts, because of their tailor‐made characteristics, have been widely reported for the synthesis of UHMWPE, but well‐designed structures are necessary, and large steric hindrance of the molecular catalysts or low polymerization temperature ( T p ) is seemed more favored. The group of Alt investigated the polymerization results of ≈100 metallocene catalysts, finding the MW of most PEs synthesized was well below the critical value of 10 6 g mol −1 .…”

“…The most notable ones are its impact resistance, abrasion resistance, lubricity, and chemical inertness, which lead it to a wide range of applications, including fibers for bullet proof armors, bearing materials for artificial joints, lining for coal chutes, as well as bumpers and sidings for ships and harbors. [1] In recent years, the versatile single-site catalysts, because of their tailor-made characteristics, have been widely reported for the synthesis of UHMWPE, [2][3][4][5] but well-designed structures are necessary, and large steric hindrance of the molecular catalysts or low polymerization temperature (T p ) is seemed more favored. The group of Alt investigated the polymerization results of ≈100 metallocene catalysts, finding the MW of most PEs synthesized was well below the critical value of 10 6 g mol −1 .…”

Synthesis and Characterization of Constrained Geometry Oxygen and Sulphur Functionalized Cyclopentadienylchromium Complexes and Their Use in Catalysis for Olefin Polymerization

“…It is mainly because the chemistry of Cr(III) is particularly difficult to study as a result of its paramagnetic nature. In recent years, some of the most significant advances in Cp-based chromium catalyst systems have been made using precatalysts that bear an additional neutral donor and bridged the Cp unit [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], so-called CGC system (CGC = Constrained Geometry Catalyst). They have already been used as efficient catalyst precursors for ethylene or 1-hexene homo (co)-polymerization, which are listed in Figure 1 .…”