The partial oxidation of propane to formaldehyde using uranium mixed oxide catalysts

A series of mixed metal oxide catalysts have been prepared and tested for the oxidation of propane and propene. Under the reaction conditions employed in these studies, Fe/Mo and U/Mo mixed oxide catalysts showing iron and uranium molybdate phases were inactive for propane and propene oxidation. A mixed U/Sb catalyst, with a USb3O10 structure, was also inactive for propane oxidation, but demonstrated the expected selective oxidation activity to form acrolein from propene. Outstanding results for the selective oxidation of propane and propene to formaldehyde were obtained using Fe/U catalysts prepared with ratios of 0.5/3 and 1/3. At 450 °C, a selectivity towards formaldehyde of 44 was achieved at 42 propane conversion. Characterisation of the Fe/U catalysts by powder X-ray diffraction (XRD) and laser Raman spectroscopy identified a UO3 phase with no evidence for an iron containing phase. Temperature-programmed reduction studies identified further reduction Features which cannot be attributed to UO3 alone. The characterisation data can be interpreted in terms of a highly dispersed iron oxide phase supported on UO3 and it is this combination which gives rise to the selective propane oxidation activity