The Oligomerization of Alkenes by Heterogeneous Catalysts

BY MEHRI SANATI, CHRISTINA HORNELL AND SVEN G. JARAS 

O Connor has written surveys of both homogeneous and heterogeneous catalysis while the reviews of Skupinska and Al-Jarallah et focus particularly on homogeneous catalysis. Recently, Minachev et al. have written about their work on the catalytic and physicochemical properties of the zeolites based on pentasils for oligomerizing lower olefins and paraffins into a mixture of aliphatic hydrocarbons of the composition Ce-Cio or into a concentrate of aromatic hydrocarbons, depending on the reaction conditions. 

The present review focuses on oligomerization in heterogeneous systems. It provides a comprehensive review and a supplement to earlier surveys of alkene oligomerization by solid catalysts. Related publications and patents to date have been reviewed and evaluated in terms of catalytic systems used, reaction conditions and product selectivity. 

However, it has been postulated that the hydrogen-transfer activity of zeolites may be undesirable due to rapid and early chain termination in oligomerization reactions, which leads to production of aromatics and coke species.  

In the reviews by both Skupinska, and Al-Jarallah et ai, it is suggested that the activities and selectivities of the catalysts are affected by strong adsorption of products, by isomerization or by a tendency to copolymerize into branched products. 

---

Alkene complexes have been prepared for nearly all the d-block transition elements. As ethene and its derivatives are good 7r-acceptors (p. 196), many of the most stable complexes are formed by elements late in the transition series. It is these elements which provide many of the catalysts, both homogeneous and heterogeneous, used to promote alkene reactions such as hydrogenation (p. 182), hydroformylation (p. 387) and oligomerization (p. 365). 

---