Oxidative Dehydrogenation of 1-Butene over Platinum Group Metal and Modified Palladium Catalysts

Abstract

The oxidative dehydrogenation of 1-butene was studied with platinum group metal catalysts. The catalytic activity decreased in the following order: Pd>Rh>Pt>Ir>Ru. However, the order of catalytic activity for the oxidative dehydrogenation plus isomerization, which were considered to proceed via a common intermediate, was in agreement with that found for oxychlorination.
The effects of additives on palladium catalysis were also studied. Halogen ion markedly suppressed carbon dioxide formation. The extent of the suppression was in the following order: F<Cl<BrzI. This trend seems to reflect the affinity between palladium and halogen ion. When bromide ion was added (as sodium salt) the selectivity of butadiene formation was about 99.9%. Alkali metal ions suppressed the isomerization of 1-butene catalyzed by acid sites on the supports, whereas they accelerated the oxidative dehydrogenation catalyzed by palladium metal. Anions other than halogen ions did not exhibit any suppression effect on carbon dioxide formation.
The suppression of carbon dioxide formation by the addition of halogen ions was considered to be not caused by the poisoning of specific active sites but to be due to the inhibition of oxygen activation which causes complete oxidation.