Fe₂O⁺ Cation Mediated Propane Oxidation by Dioxygen in the Gas Phase

The mass-selected Fe₂O⁺ cation mediated propane oxidation by O₂ was investigated by mass spectrometry and density functional theory calculations. In the reaction of Fe₂O⁺ with C₃H₈, H₂ was liberated by C−H bond activation to give Fe₂OC₃H₆ ⁺. Interestingly, when a mixture of C₃H₈/O₂ was introduced into the reactor, an intense signal that corresponded to the Fe₂O₂ ⁺ cation was present; the experiments indicated that O₂ was activated in its reaction with Fe₂O(C₃H₆)⁺ to give Fe₂O₂ ⁺and C₃H₆O (acetone or propanal). A Langmuir–Hinshelwood-like mechanism was adopted in the propane oxidation reaction by O₂ on gas-phase Fe₂O⁺cations. In comparison with the absence of Fe₂O₂ ⁺ in the reaction of Fe₂O⁺ with O₂, the ligand effect of C₃H₆ on Fe₂OC₃H₆ ⁺ is important in the oxygen activation reaction. The theoretical results are consistent with the experimental observations. The propane oxidation by O₂ in the presence of Fe₂O⁺ might be applied as a model for alkane and O₂ activations over iron oxide catalysts, and the mechanisms and kinetic data are useful for understanding corresponding heterogeneous reactions.