Oxidative dehydrogenation of n-butane to butadiene over Bi-Ni-O/γ-alumina catalyst

Oxidative dehydrogenation of n-butane to 1,3-butadiene over Bi-Ni oxide/γ-Al₂O₃ catalyst was studied with fixed bed/flow-type reactor at 400-500 °C. The γ-Al₂O₃ support itself showed activity for oxidative dehydrogenation from n-butane to n-butenes as well as partial oxidation to CO. The role of Ni oxide on γ-Al₂O₃ was confirmed that sole Ni oxide loading until 30 wt% Ni on γ-Al₂O₃ resulted higher activity and selectivity to butadiene by diminishing partial oxidation related to γ-Al₂O₃ and enhancing conversion to butadiene. The concerted effect of Bi and Ni in Bi-Ni oxide/γ-Al₂O₃ catalyst was confirmed with two methods: (1) partial or full substitution of Bi for 1/3, 2/3 and 3/3 Ni of 30 wt% Ni on γ-Al₂O₃, and (2) various amounts of Bi addition to 20 wt% Ni on γ-Al₂O₃. As for (1) Bi substitution, 10 wt% Bi-20 wt% Ni showed higher activity and selectivity than the others. As for (2) Bi addition, it until Bi/Ni = 0.82 (60 wt% Bi-20 wt% Ni) lead to suppressed CO/H₂ production and improved conversion to butadiene. 30 wt% Bi-20 wt% Ni oxide/γ-Al₂O₃ catalyst showing the highest butadiene selectivity of about 47% at 450 °C was used to confirm the relation between the state of oxygen and the reaction pathways by changing reaction condition factors, oxygen-to-butane ratio and temperature. It was revealed by catalyst characterization that the catalyst of Bi modified and Ni oxide highly loaded on γ-Al₂O₃ has high activity and selectivity for oxidative dehydrogenation of n-butane to butadiene due to either an improved Ni dispersion and redox property or a couple of weak acidity and moderate basicity.