Abstract
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•Bi–Ni oxide on γ-Al2O3 is used as catalyst for n-butane oxidative dehydrogenation to butadiene.•Sole Ni oxide loading until 30wt% results higher activity and enhanced butadiene selectivity.•10wt% Bi-20wt% Ni suppressed CO/H2 production and showed higher activity and selectivity than either 30wt% Ni or 30wt% 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 30wt% 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 30wt% Ni on γ-Al2O3, and (2) various amounts of Bi addition to 20wt% Ni on γ-Al2O3. As for (1) Bi substitution, 10wt% Bi-20wt% Ni showed higher activity and selectivity than the others. As for (2) Bi addition, it until Bi/Ni=0.82 (60wt% Bi-20wt% Ni) lead to suppressed CO/H2 production and improved conversion to butadiene. 30wt% Bi-20wt% 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.