Dimerization and isomerization of 2-methyl-1-alkenes over Re 2O 7Al 2O 3 catalyst

Abstract

Not only 2-methyl-1-hexene but also other 2-methyl-1-alkenes were dimerized selectively over a Re 2O 7Al 2O 3 catalyst activated at temperatures lower than 140°C or reduced with hydrogen gas above 300°C and also over a WCl 6Me 4Sn catalyst system in the liquid phase under atmospheric pressure and mild reaction conditions. The active sites of dimerization and isomerization of 2-methyl-1-alkenes over Re 2O 7Al 2O 3 catalyst were investigated. For this purpose, a SiO 2Al 2O 3/sulfuric acid Brønsted acid catalyst and a WCl 6 Lewis acid catalyst were also used to reveal the active sites of dimerization. These catalysts produced dimers of 2-methyl-1-alkenes selectively. The dimers and product distribution obtained from 2-methyl-1-pentene and 2-methyl-1-hexene over Re 2O 7Al 2O 3 catalyst were the same as those over WCl 6, suggesting the main active sites of dimerization are Lewis acid in character. In the reaction of 2-methyl-1-butene over Re 2O 7Al 2O 3 catalyst, the active sites of dimerization were found to be both Brønsted and Lewis acid sites. The dimers produced on Brønsted acid and Lewis acid sites differed from one another as judged by retention volumes determined by gas chromatography.