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Molecules 2017, 22(5), 751; doi:10.3390/molecules22050751

Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization

Department of Chemical Engineering, Tunghai University, Taichung 407, Taiwan
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Author to whom correspondence should be addressed.
Academic Editor: Kotohiro Nomura
Received: 24 April 2017 / Accepted: 3 May 2017 / Published: 5 May 2017
(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)
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Abstract

Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong mass transfer limitations. This study aims to improve the activity of supported CGC catalysts by using nanometer-sized silica. Ti[(C5Me4)SiMe2(NtBu)]Cl2, a “constrained-geometry” titanium catalyst, was supported on MAO-treated silicas (nano-sized and micro-sized) by an impregnation method. Ethylene homo-polymerization and co-polymerization with 1-octene were carried out in a temperature range of 80–120 °C using toluene as the solvent. Catalysts prepared and polymers produced were characterized. For both catalysts and for both reactions, the maximum activities occurred at 100 °C, which is significantly higher than that (60 °C) reported before for supported bis-cyclopentadienyl metallocene catalysts containing zirconium, and is lower than that (≥140 °C) used for unsupported Ti[(C5Me4)SiMe2(NtBu)]Me2 catalyst. Activities of nano-sized catalyst were 2.6 and 1.6 times those of micro-sized catalyst for homopolymerization and copolymerization, respectively. The former produced polymers with higher crystallinity and melting point than the latter. In addition, copolymer produced with nanosized catalyst contained more 1-octene than that produced with microsized catalyst. View Full-Text
Keywords: constrained geometry catalysts; titanium complex; silicas; nanoparticles; supports; ethylene polymerization and copolymerization; high density polyethylene; ethylene-α-olefin copolymers constrained geometry catalysts; titanium complex; silicas; nanoparticles; supports; ethylene polymerization and copolymerization; high density polyethylene; ethylene-α-olefin copolymers
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Li, K.-T.; Wu, L.-H. Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization. Molecules 2017, 22, 751.

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