Fe2 O+ Cation Mediated Propane Oxidation by Dioxygen in the Gas Phase.

Abstract

The mass-selected Fe2 O+ cation mediated propane oxidation by O2 was investigated by mass spectrometry and density functional theory calculations. In the reaction of Fe2 O+ with C3 H8 , H2 was liberated by C-H bond activation to give Fe2 OC3 H6+ . Interestingly, when a mixture of C3 H8 /O2 was introduced into the reactor, an intense signal that corresponded to the Fe2 O2+ cation was present; the experiments indicated that O2 was activated in its reaction with Fe2 O(C3 H6 )+ to give Fe2 O2+ and C3 H6 O (acetone or propanal). A Langmuir-Hinshelwood-like mechanism was adopted in the propane oxidation reaction by O2 on gas-phase Fe2 O+ cations. In comparison with the absence of Fe2 O2+ in the reaction of Fe2 O+ with O2 , the ligand effect of C3 H6 on Fe2 OC3 H6+ 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 Fe2 O+ 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.