Eric Paul Wasserman

Synchrotron XAS studies on a half-sandwich titanium-based polyethylene catalyst

Abstract A new catalyst for the copolymerization of ethylene and α-olefins, based on (η 5 -C 5 Me 5 )TiCl 3 , methanol, 2,6-di- t -butylphenol, and methylaluminoxane, is described. The polymerization behavior indicates the necessity of the hindered phenol for high activity, but does not prove that a phenoxide group exists in the coordination sphere of the active site. The titanium K-edge EXAFS spectra of mixtures of various combinations of the four components are best fit to a structure containing a short TiO bond, a Ti–arene interaction, and two alkyl carbons. XANES, and to a lesser extent X-ray photoelectron spectroscopy (XPS), spectra show that the presence of the alcohol(s) in the catalyst is correlated with higher titanium absorption energies as well as narrower peak widths.

Features of Cyclopentadienyl Metal Catalysts for Ethylene Copoly-Merization in Gas and Liquid Phase

Catalysis in gas phase reactions for the production of olefin polymers is well known in the polyolefin industry [1]. Developments in the UNIPOL® process for polyethylene, EPR/EPDM, and polypropylene continue to demonstrate the broad versatility of the process. The emergence of metallocene catalysis in many laboratories around the world has added yet another significant catalytic tool for manipulating and controlling the molecular framework of polyolefms. Selection of the appropriate metallocene catalyst, with control of ligand environment at the active site, continues to provide the basis of improved process operations and unique product opportunities.