XPS study of metallocene based catalysts for the polymerization of ethylene

• Published in: Journal of molecular catalysis. A, Chemical Vol. 101; no. 3; pp. 199 - 209
• Main Authors: Garbassi, F., Gila, L., Proto, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.08.1995; Elsevier
• Subjects: Applied sciences; Ethylene; Exact sciences and technology; Hafnium; Metallocenes; Organic polymers; Photoemission; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Titanium; XPS; Zirconium; Zirconium; Photoemission; Ethylene; Hafnium; Polymerization; Titanium; XPS; Metallocenes; Polyethylene; Ziegler Natta catalyst; Titanium complex; Hafnium complex; Complex catalyst polymerization; Zirconium complex; Surface analysis; Experimental study; Metallocene; Electronic structure; Structure activity relation; Olefin polymer; Catalyst activity
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/1381-1169(95)00065-8

X-ray photoelectron spectroscopy (XPS) has been applied to the study of a series of metallocene catalysts, containing Zr, Ti or Hf, for the polymerization of ethylene. Surface atomic compositions, binding energies and valence band (VB) spectra have been measured. Surface compositions were found to be more or less similar to the expected values on the basis of molecular structure depending on the stability of compounds vs. air contact. XPS analyses after air exposure showed a marked tendency of metal-Cl bonds to be substituted by metal-O bonds. Binding energy of zirconium was found to be rather sensitive on the overall electron-attractive effect of ligands, with the following energy scale: ZrCl 4 > Cp 2ZrF 2 > CpZrCl 3 > Cp 2ZrCl 2 = (Cp 2ZrCl) 2O > Cp 2Zr(NET 2) 2. A relationship was found with catalytic activity, which seems to be favoured by a low binding energy value of Zr. VB spectra have been discussed, showing peculiar features depending on the molecular structure.