Selective Oxidation of n-Butane and Butenes over Vanadium-Containing Catalysts

The oxidative dehydrogenation (OXDH) of n-butane, 1-butene, and trans-2-butene on different vanadia catalysts has been compared. MgO, alumina, and Mg–Al mixed oxides with Mg/(Al+Mg) ratios of 0.25 and 0.75 were used as supports. The catalytic data indicate that the higher the acid character of catalysts the lower is both the selectivity to C4-olefins from n-butane and the selectivity to butadiene from both 1-butene or trans-2-butene. Thus, OXDH reactions are mainly observed from n-butane and butenes on basic catalysts. The different catalytic performance of both types of catalysts is a consequence of the isomerization of olefins on acid sites, which appears to be a competitive reaction with the selective way, i.e., the oxydehydrogenation process by a redox mechanism. Infrared spectroscopy data of 1-butene adsorbed on supported vanadium oxide catalysts suggest the presence of different adsorbed species. O-containing species (carbonyl and alkoxide species) are observed on catalysts with acid sites while adsorbed butadiene species are observed on catalysts with basic sites. According to these results a reaction network for the oxydehydrogenation of n-butane is proposed with parallel and consecutive reactions.