Isomerization and disproportionation of olefins over tungsten oxides supported on various oxides

Abstract

The isomerizations of 1-butene and cyclopropane and the disproportionations of 1-butene, propylene and ethylene were investigated over tungsten oxides supported on MgO, Al 2O 3, SiO 2, TiO 2 and ZrO 2. A combination of tungsten oxide with TiO 2, in which the amount of tungsten oxide was varied from 1 to 20 mol%, resulted in a generation of acid sites. The acid properties were well correlated with the catalytic activity in the isomerization of 1-butene. The production of acid sites also caused a marked decrease in the cis trans ratio in 2-butene formed. The order of the activity of various supported catalysts for the isomerization of cyclopropane was WO 3Al 2O 3 > WO 3ZrO 2 > WO 3TiO 2 > WO 3 ⪢ WO 3SiO 3 = WO 3MgO = 0, whereas that for the disproportionation of propylene was WO 3TiO 2 ≳ WO 3ZrO 2 > WO 3Al 2O 3 > WO 3SiO 2 > WO 3MgO = WO 2 = 0. An optimum activity was obtained for 5 mol% tungstem oxide on WO 3TiO 2. During the disproportionation reaction of propylene over WO 3TiO 2, the formation of i-butene was found. Production of propylene was also found in the reaction of ethylene over WO 3TiO 2. The formation i-butene from propylene and propylene from ethylene suggests that the reaction takes place via carbene intermediates.