Polymerization of ethylene catalyzed by diethylaluminum chloride and titanium (<scp>III</scp>) acetylacetonate

Abstract

Abstract Catalysts for the polymerization of ethylene were prepared from titanium (III) acetylacetonate and diethylaluminum chloride. Titanium (III) acetylacetonate is of interest because it is soluble in hydrocarbon solvents used as polymerization media. As its oxidation product oxobisacetylacetonatotitanium (IV) is also hydrocarbon‐soluble, this system provides a vehicle for studying the effects of a change in valence on catalyst activity without an accompanying change of state, as occurs with titanium halides. Relatively high molar ratios (&gt;20:1) of aluminum alkyl to titanium compound were required to give active catalysts. Precipitates generally formed in the catalyst mixtures, although dilute catalyst solutions in which no precipitate was visible still initiated polymerization. Catalyst mixtures were observed to undergo certain changes on standing. Light‐scattering studies indicated an increase in catalyst particle size, and a gas identified as ethane was evolved. These changes were accompanied by a reduction in activity of the catalyst. Parallel polymerization tests were run for a comparison of catalysts prepared from titanium(III) acetylacetonate and catalysts prepared from oxobisacetylacetonatotitanium(IV). There was essentially no difference in yield or properties of polymer prepared using the two catalyst systems. The evidence suggests that both the trivalent and tetravalent titanium compounds yield the same catalytic intermediate when reacting with diethylaluminum chloride.