Ferrite spinels as catalysts in the oxidative dehydrogenation of butenes

Abstract

Both CoFe 2O 4 and CuFe 2O 4 spinels are active catalysts for oxidative dehydrogenation of n-butenes to butadiene. However, both suffer from their tendency to catalyze total oxidation as well. Neither is an effective n-butene isomerization catalyst, even at high temperatures. Surface and lattice oxygen atoms participate in the reactions, and the steady state in the presence of gaseous oxygen, at least for CoFe 2O 4, is near the totally oxidized state. Selectivity for the dehydrogenation reaction is strongly dependent on the presence of gaseous oxygen in the case of the Co catalyst, although the selectivity over the Cu catalyst is not a strong function of gaseous oxygen. The kinetics are not simple; the pressure dependencies are less than first order in both butene and oxygen pressures and the reactions are inhibited by the presence of butadiene. CH bond cleavage is probably involved in the rate-determining step of all reactions, although the reactions showed some characteristics of both interand intramolecular mechanisms.