Donor/Acceptor Metallocenes: A New Structure Principle in Catalyst Design

Starzewski, K. A. Ostoja; Kelly, W. Mark; Stumpf, Andreas; Freitag, D.

doi:10.1002/(sici)1521-3773(19990816)38:16<2439::aid-anie2439>3.3.co;2-5

Cited by 16 publications

(22 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[ 7–10 ] Then, it was reported that metallocene catalysts immobilized on special supports were successfully used to produce UHMWPE. [ 11 ] The conventional metallocene catalysts such as CpTiCl 3 and CpZrCl 2 were reported to produce UHMWPE when immobilized on some special supports. [ 12,13 ] However, the processability of UHMWPE was poor because of the high melt viscosity which was caused by the extensive entanglement among molecular chains.…”

Section: Introductionmentioning

confidence: 99%

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Wang

Jin

Liu

et al. 2020

Macro Chemistry & Physics

View full text Add to dashboard Cite

Polyethylene (PE) with bimodal molecular weight distribution (MWD) has drawn attention from both academia and industry. Bimodal PE combines great processability with outstanding mechanical properties. The single‐reactor technology process through a dual site catalyst system is an optimal strategy considering the economic effect and the manufacturing technique. To satisfy the demand of the dual site catalyst system for producing bimodal PE, novel SiO2‐supported chromium oxide/chromocene dual site catalysts for ethylene polymerization are successfully synthesized and systematically investigated. The novel catalysts are prepared by using the residual hydroxyl groups on the surface of SiO2‐supported chromium oxide (CrOx) Phillips catalyst to introduce chromocene. It is found that the novel dual site catalysts combine the advantages of chromocene catalyst (S‐9 catalyst) and Phillips CrOx/SiO2 catalyst. The activities of the dual site catalysts are doubled at least compared to the S‐9 catalyst due to the high activity of the CrOx active center. The products of the dual site catalysts show significantly high molecular weight (MW) with bimodal MWD through ultrahigh molecular weight polyethylene/high‐density polyethylene in reactor alloys. The dual site catalysts show great hydrogen response according to the hydrogen experiment results, which lead to the easy control of MW.

show abstract

Section: Introductionmentioning

confidence: 99%

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Wang

Jin

Liu

et al. 2020

Macro Chemistry & Physics

View full text Add to dashboard Cite

show abstract

“…[27] Metallocene catalysts were also used to produce UHMWPE, but the processes were much more complex than Ziegler-Natta catalyst. [28] When immobilized on particular supports (carbon nanotubes and graphene nanoplatelet), the metallocene catalysts such as CpTiCl 3 and CpZrCl 2 could produce UHMWPE. [29,30] The metallocene catalysts through single activity site, which were different from Ziegler-Natta catalyst, made the reaction rates stable and the products have narrow MWD.…”

Section: Introductionmentioning

confidence: 99%

Study of Silica‐Supported Chromocene Catalysts for Ethylene Polymerization

Wang

Gao

et al. 2020

Macro Chemistry & Physics

View full text Add to dashboard Cite

Ultrahigh molecular weight polyethylene (UHMWPE) has drawn great interest from researchers because it possesses many excellent properties such as superb strength and impact resistance, which other polyolefin cannot achieve. A silica‐supported chromocene catalyst, for the production of UHMWPE, is successfully developed. The polyethylene (PE) produced by the chromocene catalyst can achieve a molecular weight (MW) of over 3 × 106 g mol−1 with narrow molecular weight distribution (MWD) a value of approximately three. The activity calculated by Cr per unit reaches the maximum when the loading of Cr is 1.7 wt%. With the increasing loading of chromocene, the MW shows a small increase and the MWD becomes narrower. The chromocene catalyst for ethylene polymerization also shows a significant hydrogen response. With 0.01 MPa hydrogen added into the ethylene polymerization, the MW of the PE decreases immensely to only 0.7 × 106 g mol−1 and the MWD is broadened from <3 to ≈12. If the amount of hydrogen increases, the MW continues to decrease and the MWD becomes wider. The MW of the PE produced by the chromocene catalyst can be regulated easily by adjusting the amount of hydrogen.

show abstract

“…Metallocene catalysts could also be used for UHMWPE, but they were not able to synthesize UHMWPE with as much ease as ZN catalysts did . The polymerization results of ≈100 different metallocene catalysts were surveyed by Alt and Köppl and indicated that the MW of the PEs produced was mostly well below the critical value of 10 6 g mol −1 .…”

Section: Introductionmentioning

confidence: 99%

“…Resconi et al reported a hindered and covalently bridged meso‐ethylene‐bis(4,7‐dimethyl‐1‐indenyl) zirconium dichloride catalyst which was able to synthesize UHMWPE at 70 °C . Starzewski et al synthesized a series of bridged donor/acceptor metallocene catalysts with hindered structures to produce UHMWPE at temperature higher than 80 °C . Besides ZN and metallocene catalysts, several nonmetallocene catalysts were also reported to synthesize UHMWPE.…”

Section: Introductionmentioning

confidence: 99%

The First Vanadium-Oxide-Based UHMWPE Catalyst Supported on Chemically Modified Silica Gel

Jin

Cheng

et al. 2017

Macromol. Chem. Phys.

View full text Add to dashboard Cite

Novel vanadium‐oxide‐based catalysts supported on alumina, zirconia, or titania‐modified silica, which are able to synthesize ultrahigh molecular weight polyethylene (UHMWPE), are successfully developed. Compared with the unmodified silica supported catalyst, the activities of the modified catalysts are substantially enhanced. By changing the polymerization temperature (Tp) from 90 to 60 °C, the molecular weight of the produced UHMWPE can be easily regulated from 2 × 106 to more than 6 × 106 g mol−1. It is the first time that chloride‐free nonsingle site catalysts have been developed to synthesize UHMWPE within such a broad range of Tp. Catalyst characterization by NH3‐temperature‐programmed desorption and pyridine‐Fourier transform infrared spectroscopy reveals that the modified catalysts have increased acidity derived from both Lewis and Brønsted acid sites. The X‐ray photoelectron spectroscopy characterization indicates that the vanadium on the modified catalysts is more electron deficient. Thus, the acidity of the catalysts and the electronic state of the vanadium play a critical role in determining the activity of the vanadium active sites for ethylene polymerization.

show abstract

Donor/Acceptor Metallocenes: A New Structure Principle in Catalyst Design

Cited by 16 publications

References 0 publications

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Study of Silica‐Supported Chromocene Catalysts for Ethylene Polymerization

The First Vanadium-Oxide-Based UHMWPE Catalyst Supported on Chemically Modified Silica Gel

Contact Info

Product

Resources

About

Donor/Acceptor Metallocenes: A New Structure Principle in Catalyst Design

Cited by 16 publications

References 0 publications

Novel SiO2‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Novel SiO2‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Study of Silica‐Supported Chromocene Catalysts for Ethylene Polymerization

The First Vanadium-Oxide-Based UHMWPE Catalyst Supported on Chemically Modified Silica Gel

Contact Info

Product

Resources

About

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys

Novel SiO₂‐Supported Chromium Oxide/Chromocene Dual Site Catalysts for Synthesis of Bimodal UHMWPE/HDPE in Reactor Alloys