Dimerisation of propene catalysed by transition-metal compounds and complexes

Abstract

Propene dimerisation has been studied using catalysts of the following types: (a) aluminium alkyl halides, (b) cobalt (or nickel) halide–aluminium alkyls, (c) cobalt chloride–aluminium chloride and related systems, (d) cobalt chloride–aluminium chloride–aluminium alkyls, and (e) nickel oxide–silica–alumina.

Many of these systems were found to have very high activities. The presence of the transition-metal salts led to high selectivity to dimerisation, selectivity exceeding 95% in some cases. Hexene dimer products were remarkably similar in all cases and at a reaction temperature of 40–80° consisted of ca. 30% n-hexenes and 70% methylpentenes. Selectivity to n-hexenes increased with temperature to ca. 50% at 150°. An attempt is made to rationalise these results in a reaction mechanism involving cationic catalysis.