XPS study of the interaction of titanium species with internal electron donors on MgCl2-supported Ziegler catalysts

Two types of MgCl2-supported Ziegler catalysts prepared by a similar proced ure with different internal electron donors were analyzed using X-ray photo electron spectroscopy (XPS) to elucidate the interaction of the titanium sp ecies with the internal donors. The XPS measurement was also performed with an internal donor-free supported catalyst and TiCl4 . ester complexes. The binding energies the Ti-2p3/2 peak in the three supported catalysts were a lmost the same in spite of the difference in the internal donor. The higher values of the binding energy in the TiCl4 . ester complexes, compared with the supported catalysts, indicated that the TiCl4 . internal donor complex itself did not exist on the surface of the supported catalysts. The compar ison of the binding energies among the supported catalysts after the reacti on with triethylaluminium (TEA) showed that the reduction of the titanium s pecies on the supported catalysts proceeded at the same level, regardless o f the kind of the internal donor and of the catalyst preparation method. Fr om the results obtained in this study, it was concluded that the internal e lectron donor existed free from titanium species on the supported catalysts , but the nature of the active sites was affected by the change in the envi ronment through the interaction of the donor with MgCl2. (C) 1999 Elsevier Science B.V. All rights reserved.