Ammoxidation of propane to acrylonitrile over silica-supported Fe-Bi nanocatalysts

• Cluster-derived Fe3BiOx/SiO2 is an effective catalyst for propane ammoxidation.
• 2 nm particles are formed on the surface of this material under reaction conditions.
• These particles incorporate Fe3+ and Bi3+ components with a 3:1 Fe/Bi atomic ratio.
• Co-impregnated Fe-Bi/SiO2 is low active for propane ammoxidation.
• Larger particles with surfaces enriched with Fe are formed in this material.

Ammoxidation of propane to acrylonitrile was examined over a Fe3BiOx/SiO2 sample prepared by thermal decarbonylation of [Et4N][Fe3(CO)10(μ3-Bi)] on the surface of mesoporous silica. Catalytic measurements performed at 500 °C showed that this sample yields 49% acrylonitrile selectivity at 36% propane conversion when a 5.5%C3H8/30%O2/11%NH3/He balance reaction mixture was used at a GHSV of 1360 h−1. HRSTEM, EDS, and XPS measurements indicate that mixed Fe3BiO6 oxide particles less than 2 nm in size were formed on the surface of this material under reaction conditions. A Fe/Bi atomic ratio in these particles is approximately 3:1 and the Fe and Bi ions both are in the +3 oxidation state. A Fe-Bi/SiO2 sample prepared by co-impregnation of individual Fe and Bi salts had very low activity and low selectivity for acrylonitrile formation from propane under similar experimental conditions due to larger sizes of particles formed under reaction conditions and enrichment of their surface with Fe.

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