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

•Bi–Ni oxide on γ-Al2O3 is used as catalyst for n-butane oxidative dehydrogenation to butadiene.•Sole Ni oxide loading until 30 wt% results higher activity and enhanced butadiene selectivity.•10 wt% Bi-20 wt% Ni suppressed CO/H2 production and showed higher activity and selectivity than either 30 wt% Ni or 30 wt% Bi.•Bi addition results in a couple of weak acidity and moderate basicity with Ni dispersion and redox improvement.

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.

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