Ion cyclotron resonance study of CO oxidation in the gas phase in the presence of rhenium cations with carbonyl and oxygen ligands. Comparison with heterogeneous catalysis

Abstract

Gas-phase oxidation of CO in the presence of rhenium cations with carbonyl and oxygen ligands has been studied by Fourier transform ion cyclotron resonance (FT-ICR) spectrometry. Rhenium cations have been generated by the electron impact of Re2(CO)10 vapour. Contrary to the unreactive rhenium ions, rhenium monocarbonyi ions have been found to react with O2 molecules yielding rhenium monoxide ions and CO2 molecules. ReO+ ions are subsequently oxidized with O2 to di- and trioxide ions. The bond energies in rhenium oxide ions were estimated as D°(Re+−O)=104±14, D°(ReO+−O)<118, D°ReO 2 + −O)=122±4 kcal/mol. Simultaneous addition of CO and O2 molecules to the reaction volume leads to the gas-phase catalytic oxidation of CO with pairs of rhenium oxide ions ReO 3 + /ReO 2 + serving as the oxidized and reduced forms of the catalyst. The mechanisms of the above reactions are discussed in connection with that for oxidation of CO over solid oxide catalysts.