DIMERIZATION OF ETHYLENE TO BUTENE-1 CATALYZED BY TI(OR')4-ALR3

The catalytic dimerization of ethylene stands as the most selective and economical route to polymerization grade butene-1. This approach is currently exemplified by the IFP-SABIC process for the production of butene-1 wherein ethylene is dimerized over the modified Ziegler-Natta homogeneous catalysts Ti(OR')4-AlR3 (R'=C1-C-8 alkyl or aryl, R=C1-C6 alkyl). The mass of the published patents and the technical literature dealing with the ethylene dimerization over various transition metal based complexes is overwhelming. Therefore, the literature taken into account in this review was selected in order to give more weight to fundamental studies and less to patent claims. This paper is dedicated to discussing the chemical perspectives of the dimerization reaction over the titanium-based catalytic system with its main objective being to get a more decisive picture on the performance of these catalysts. This review paper identifies the components of this homogeneous system and discusses, in fair detail, the factors controlling its selectivity to butene-1. Other different themes covered include: structure of the active species, kinetics, mechanistic considerations and the principal reaction parameters. Additionally, this survey is supplemented by a summarized account for the corresponding supported titanate catalysts and their usage as a dimerization component in the dual functional catalytic systems.