XPS study of the interaction of titanium species with internal electron donors on MgCl 2-supported Ziegler catalysts

Abstract

Two types of MgCl 2-supported Ziegler catalysts prepared by a similar procedure with different internal electron donors were analyzed using X-ray photoelectron spectroscopy (XPS) to elucidate the interaction of the titanium species with the internal donors. The XPS measurement was also performed with an internal donor-free supported catalyst and TiCl 4·ester complexes. The binding energies the Ti 2p3/2 peak in the three supported catalysts were almost the same in spite of the difference in the internal donor. The higher values of the binding energy in the TiCl 4·ester complexes, compared with the supported catalysts, indicated that the TiCl 4·internal donor complex itself did not exist on the surface of the supported catalysts. The comparison of the binding energies among the supported catalysts after the reaction with triethylaluminium (TEA) showed that the reduction of the titanium species on the supported catalysts proceeded at the same level, regardless of the kind of the internal donor and of the catalyst preparation method. From the results obtained in this study, it was concluded that the internal electron donor existed free from titanium species on the supported catalysts, but the nature of the active sites was affected by the change in the environment through the interaction of the donor with MgCl 2.