DIMERIZATION AND ISOMERIZATION OF 2-METHYL-1-ALKENES OVER RE2O7-AL2O3 CATALYST

Not only 2-methyl-1-hexene but also other 2-methyl-1-alkenes were dimerized selectively over a Re2O7-Al2O3 catalyst activated at temperatures lower than 140-degrees-C or reduced with hydrogen gas above 300-degrees-C and also over a WCl6-Me4Sn 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 Re2O7-Al2O3 catalyst were investigated. For this purpose, a SiO2-Al2O3/sulfuric acid Bronsted acid catalyst and a WCl6 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 Re2O7-Al2O3 catalyst were the same as those over WCl6, suggesting the main active sites of dimerization are Lewis acid in character. In the reaction of 2-methyl-1-butene over Re2O7-Al2O3 catalyst, the active sites of dimerization were found to be both Bronsted and Lewis acid sites. The dimers produced on Bronsted acid and Lewis acid sites differed from one another as judged by retention volumes determined by gas chromatography.