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The oxidative dehydrogenation of n-butane was investigated over a highly selective (Ni, Fe, Co)–Bi–O/γ-Al2O3catalyst with kinetic studies. The transient response method with O2concentration was also utilized to study the oxygen species responsible for dehydrogenation and cracking pathways. Power law models were utilized for the reactions. The activation energies were obtained in the order 34.4 < 68.8 < 88.5 kJ/mol, and pre-exponential factors of 0.857, 1.930, and 0.198 mol/gcat.min for the first-step dehydrogenation, second-step dehydrogenation, and cracking, respectively, were obtained. The quantitative fixation reveals that the butadiene selectivity mainly reflects the pre-exponential factor as the concentration/accessibility of the active sites.

The effect of metal oxide species in (Ni, Fe and/or Co) oxide-Bi 2 O 3 over gamma-alumina support was investigated for n-butane oxidative dehydrogenation. Partial substitution of Ni up to 50% by Fe improved butadiene selectivity while same substitution with Co increased n-butane conversion. The ternary Ni-Fe-Co system (10 wt% Ni–5 wt% Fe–5 wt% Co–30 wt% Bi-O/gamma-Al 2 O 3 ) showed the highest butadiene selectivity of 46.3% at n-butane conversion of 30%. The acid-base sites preferably adjusted by ternary main metal combination in hierarchical cohabitation of metal (Ni, Fe and Co) oxide, Bi 2 O 3 and gamma-Al 2 O 3 cooperate to accelerate butadiene selectivity at both 1st and 2nd step dehydrogenations due to an increased H 2 abstraction and 1-butene intermediate adsorption. [ABSTRACT FROM AUTHOR]