Electrochemical synthesis of titanium‐based Ziegler‐Natta catalysts and their potential application in ethylene homo‐ and copolymerization

Abstract

AbstractHighly active Ziegler‐Natta catalysts have been synthesized using an electrochemical process in their preparation, with the aim of producing selectively titanium(III) species from TiCl4. The use of an undivided cell, an aluminium anode and a halogenated solvent (dichloromethane or 1,2‐dichloroethane), has allowed the production in situ of chloroalkyl aluminium species, by cathodic reduction of TiCl4, thus giving rise to a new Ziegler‐Natta catalytic combination. The possibility of scale up for this lectrochemical synthesis has been clearly shown. The Ti/Al system was modified so as to enhance its activity, first by adding a soluble dialkylmagnesium compound and then a soluble vanadium compound such as VOCl3. This Ti/Al/Mg/V highly active system was used under different conditions: in a hydrocarbon medium at low (80°C) and high (200°C) temperature and also under supercritical conditions in a continuous high‐pressure autoclave reactor, to produce homoor copolymers of ethylene with α‐olefins. Compared to similar heterogeneous catalysts obtained by comilling, the observed activities are shown to be very much improved, especially under high pressure and high temperature conditions. This may be related to the very narrow granular distribution centered at 2,5‐3 μm, compared to a much broader distribution (centered at 6 μm) obtained with the comilled catalyst.