Dimerization of Olefins with Alkali Metals

Free or supported alkali metals readily dimerize propene to a mixture of 2-methylpentenes at 420 — 470 K and 7.0 MPa. As support materitds, silica, a-alumina, oxides or carbonates of alkali and alkaline earth metals are used. The compounds of graphite intercalated by the alkali metals are also used.  

The products of propene dimerization using alkali metals dispersed on a variety of supports are given in Table 4.18. The reactions were performed over a support containing 0.1 mole of dispersed alkali metal at 423 K and about 10 MPa pressure. The main product is 4-methyl — 1-pentene, as expected from the allylic carbanion addition to double bond. 

The selectivity to 4-methyl — 1-pentene increases with reaction temperature, while the catalyst life decreases with increasing the temperature. 

Pis man et studied dimerization using dispersed sodium and potassium on various supports and found that sodium deposited on potassium carbonate is the most effective catalyst. 

---