Abstract
Ethylene and propylene polymerization on immobilized catalysts of composition MMT-H2O/AlR3/Zr-cene (MMT = montmorillonite) and on the corresponding homogeneous catalysts of composition Zr-cene-MAO (Zr-cene = rac-Et(Ind)2ZrCl2, rac-Me2Si(Ind)2ZrCl2, rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2, rac-1-(9-η5-Flu)2-(5,6-Cp2-Me-1-η5-Ind)Et]ZrCl2) is considered. Here, the activating support for the zirconocenes is montmorillonite containing methylaluminoxane or isobutylaluminoxane synthesized directly on the monmorillonite surface by the partial hydrolysis of an alkylaluminum (AlMe3, Al(i-Bu)3, Al(i-Bu)2H) with the mobile water of the support (MMT-H2O/AlR3). The MMT-H2O/AlR3 supports are demonstrated to be effective activators for ansa-zirconocenes. The catalytic properties of the immobilized systems (process kinetics and efficiency, the molar mass of the resulting polymer, and the structure of the macromolecules) depend on the activating support and the zirconocene precatalyst. The complexes of the MMT-H2O/Al(i-Bu)3 support with all zirconocene precatalysts are more active in propylene polymerization than the same complexes of MMT-H2O/AlMe3. The zirconcenes immobilized on MMT-H2O/AlR3 afford polyethylene and polypropylene with a higher molar mass than the corresponding homogeneous systems. Furthermore, immobilization causes activesite heterogeneity. As compared to the homogeneous single-site catalysts of composition Zr-cene-MAO, the corresponding catalysts immobilized on MMT-H2O/AlR3/Zr-cene are more stereospecific in the case of rac-Me2Si(Ind)2ZrCl2 (C2 symmetry) and are less stereospecific in the case of rac-[1-(9-η5-Flu)2-(5,6-Cp-2-Me-1-η5-Ind)Et]ZrCl2 (Cs symmetry).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.