In Situ EPR Monitoring of Chromium Species Formed during Cr−Pyrrolyl Ethylene Trimerization Catalyst Formation

Abstract

The catalyst systems Cr(acac) 3 /pyrrole/AlEt 3 /AlEt 2 Cl and Cr(EH) 3 /pyrrole/AlEt 3 /AlEt 2 Cl in cyclohexane (EH = 2-ethylhexanoate), modeling the Phillips ethylene trimerization catalyst, have been studied by EPR spectroscopy. The effect of various components of these catalyst systems on the concentration of Cr(III) and Cr(I) species and ethylene trimerization activity has been investigated. The relationship between the trimerization data and the nature of the chromium species present in the reaction solution has been studied.