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XPS study of Al‐Alkyl effect on Ziegler–Natta catalytic system

X‐ray photoelectron spectroscopy was performed on Ziegler–Natta catalysts to elucidate the effect of aluminum alkyl compounds (Al‐Alkyl) on TiClx/MgCl2/THF catalytic system. Chemical structure and element composition changes of catalysts were studied and various reduction activity of Al‐alkyl on catalysts was identified in different processes. The analytical results indicate that XPS is an acceptable method to measure titanium valence in Al‐alkyl‐ZN catalysts with a proper sample protection method. The XPS results demonstrate that the Al‐alkyl treatment of ZN catalysts could influence the chemical state of titanium dramatically. In Method A, the valence of Ti was reduced to Ti3+ partially, and the contents of Ti3+ increased with the increasing amount of DC, but Ti2+ was absent. With same amount of Al%, combination of DC and THA has better reduction effect than DC with Method B. Copyright © 2011 John Wiley & Sons, Ltd.