Surface Reactions of Oxygen Ions. 5. Oxidation of Alkanes and Alkenes by O2- on MgO

Article abstract of DOI:10.1021/j100460a022

Stoichiometric reactions between superoxide ions on MgO and simple hydrocarbons were observed at 175 deg C, although the O2^- ions were much less reactive than either O^- or O3^- ions.Several types of oxygen-containing products were formed, as well as other hydrocarbons and CO2.The reaction of propylene with O2^- gave no gaseous product at 175 deg C; however, at elevated temperatures acetaldehyde and methanol were obtained.Following the reaction of propane with O2^-, acetone was detected at 175 deg C in addition to acetaldehyde and methanol which were observed at higher temperatures.With 1-butene as the reactant, 2-butanol was formed together with methanol, acetaldehyde, and acrolein above 300 deg C.Infrared spectra of surface intermediates indicate that the reaction of O2^- with propylene at 175 deg C resulted in the simultaneous formation of formate and acetate ions which are consecutively converted to carbonate ions at elevated temperatures.It is proposed that hydrogen atom abstraction is the initial step in the reaction of O2^- with simple hydrocarbons.The resulting radicals react with lattice oxygen ions forming carboxylate ions or with HO2^- ions forming alkoxy or epoxide intermediates.