title: Spectroscopic investigation of heterogeneous Ziegler-Natta catalysts: Ti and Mg chloride tetrahydrofuranates, their interaction compound, and the role of the activator.
abstract: X-ray powder diffraction (XRPD), Infrared, Raman, and UV/Vis spectroscopy have been used to investigate the structural, vibrational, and optical properties of Ti and Mg chloride tetrahydrofuranates as precursors of heterogeneous Ziegler-Natta catalysts for polyethylene production; as well as their interaction compound (pro-catalyst) and the final catalyst obtained after interaction with the AlR(3) activator. Although the structure of the precursors and of the pro-catalyst were well known, that of the catalyst (obtained by reaction of the pro-catalyst with AlR(3)) was not easily obtainable from XRPD data. IR and Raman spectroscopy provided important information on tetrahydrofuran (thf) coordination and on the ν(M-Cl) region; whereas UV/Vis spectroscopy gave the direct proof on both the formal oxidation state and the coordination environment of the active Ti sites. Those presented herein are among the first direct experimental data on the structure of the active Ti sites in Ziegler-Natta catalysts, and can be used to validate the many computational studies that have been increasing exponentially in the last few decades.
authors.affiliation: Department of Inorganic, Physical and Materials Chemistry, NIS Centre of Excellence and INSTM Unità di Torino, University of Torino, Via Quarello 11, 10135 Torino, Italy.
authors.forename: Kalaivani
authors.initials: K
authors.lastname: Seenivasan
authors.forename: Anna
authors.initials: A
authors.lastname: Sommazzi
authors.forename: Francesca
authors.initials: F
authors.lastname: Bonino
authors.forename: Silvia
authors.initials: S
authors.lastname: Bordiga
authors.forename: Elena
authors.initials: E
authors.lastname: Groppo