Silica-Supported Zirconocene/(Perfluorophenyl)borate Catalyst for Propylene Polymerization: DRIFTS Study of the Catalyst Formation and Surface Species
Journal of Molecular Catalysis A: Chemical
||FTIRS, Perfluoroarylborate activator, Propylene polymerization, Supported zirconocene catalysts
Boreskov Institute of Catalysis SB RAS
IR spectroscopy has been used to study the interaction of silica with PhNEt2 (N) and B(C6F5)3 (B) and subsequent interaction of the support SiO2/[N + B] with dimethylzirconocene Me2Si(2-Me-Ind)2ZrMe2 (“Zr”). The data were obtained on the composition of the surface compounds appeared at both stages of catalyst synthesis.
It has been shown that (B) and (N) interact with OH groups of silica to form ionic pair [Hsingle bondNR3]+[(C6F5)3Bsingle bondOsingle bondSitriple bond; length of mdash]− (IP-1). Cation fragment of this pair contains highly reactive Nsingle bondH bond with a.b. at 3230 cm−1. It has been found that Nsingle bondH groups in a part of IP-1 complexes react with neighboring OH groups of silica by hydrogen bonding that gives complexes IP-2. It has been shown that “Zr” complexes interact both with complexes IP-1 and IP-2. As “Zr” reacts with IP-1, zirconium ionic complexes IP-3 containing Zrsingle bondMe bond are formed on silica. These complexes are suggested to be the precursor of the polymerization active sites. The reaction of “Zr” with IP-2, most likely, produces surface zirconium compound containing no Zrsingle bondMe bonds and inactive for propylene polymerization.