金属酸化物上のO^-ラジカルの化学

抄録

The formation of O^- radical over various metal oxides, its reactivity, and catalytic oxidations using O^- as an oxidant have been described. It is confirmed by ESR, XPS, TPD etc. that O^- radical can be generated through decomposition or charge transfer processes of O₂, O^2-, OH^-, or N₂O. Respective characters of O^- on various metal oxides, that is, g-values of ESR spectra and desorption temperatures etc., were summarized. Among oxygen species such as O^-, O^-₂ and O^-₃, O^- radical shows the highest activity for stoichiometric oxidations of hydrocarbons and the order of reactivities has been clarified to be O^->O^-₃>O^-₂ independent of metal oxides. Reaction schemes of O^- radical with hydrocarbons have been proposed on the basis of the ESR, IR, and TPD observations and also been compared with those of O^-₂ and O^-₃. In the last section, catalytic oxidations of hydrocarbons by nitrous oxide, which decomposes readily and selectively to yield an O^- radical on metal oxide surfaces, have been outlined, including new types of catalytic oxidations such as one-step conversions of methane into methanol, of alkanes into alkenes, and of benzene into phenol.