Oxidative dehydrogenation of n-butane to butadiene catalyzed by new mesoporous mixed oxides NiO-(beta-Bi₂O₃)-Bi₂SiO₅/SBA-15 system

NiO-beta-Bi₂O₃-Bi₂SiO₅/SBA-15 catalysts, containing 10−20 wt% Ni and 10−30 wt% Bi loaded as metal weight on mesoporous SiO₂ support (SBA-15), were utilized for the oxidative dehydrogenation of n-butane to butadiene, comparing from the viewpoint of Bi oxide phase and combination balance with Ni oxide and the support. Bi₂SiO₅ and beta-Bi₂O₃ phases change depending on Ni/Bi ratio. “Reverse core-shell” structure with uniform mesoporosity catalytically active for the oxidative dehydrogenation of n-butane to butadiene was successfully synthesized with semi-dry conversion method. The shell was formed as Bi₂SiO₅/SBA-15 by partially dissolving an array of silanol inside SBA-15 mesopores with impregnated bismuth nitrate. The Bi₂SiO₅ of the shell was increased by co-impregnated nickel nitrate. The layered core faced to mesopore was formed as catalytically active NiO/beta-Bi₂O₃ on the shell. The degrees of formation Bi₂SiO₅ and beta-Bi₂O₃ reflected in the butadiene selectivity through changing the reducibility and dispersion properties. The catalyst with moderate loading of 20 wt% Ni and 10 wt% Bi exhibited a high advantage in the n-butane conversion: 30 % and butadiene selectivity: 49 % at 450 °C compared to the less and excess loaded catalysts. The catalytic performance of other mesoporous silica support catalysts also changed differently depending on Bi₂SiO₅ and beta-Bi₂O₃ phases.