Transformations o f 1,5-hexadiene and 1,3,5-hexatriene on aluminum, gallium, and indium oxides

Abstract

1. On the example of the transformations of 1,5-hexadiene at 450 and 520°, and of 1,3,5-hexatriene at 300 and 450°, on aluminum, gallium, and indium oxides it was shown that Al2O3 has a very weak, while Ga2O3 and In2O3 have a strong aromatizing (dehydrogenating) ability, but one that is less than that of Cr2O3. All three oxides catalyze migration of the double bond in dienic hydrocarbons. The main transformation products of 1,5-hexadiene are benzene and hexadienes, which are isomeric with the starting material, and benzene and cyclohexadienes in the case of 1,3,5-hexatriene. Hydrogenation products are also formed, as well as small amounts of hydrocarbons with a five-membered ring. 2. The obtained results can be explained by the fact that the formation of benzene from aliphatic C6 hydrocarbons on Ga2O3 and In2O3 proceeds by the same scheme as on other oxide catalysts. 3. The change in the aromatizing (dehydrogenation) ability when going from Al2O3 to Ga2O3 and In2O3 correlates with their ability to be reduced and is opposite to the change in the heats of formation of these oxides.