Reaction of methane with nitrous oxide over magnesium oxide at low temperatures

Abstract

Partial oxidation of CH₄ by N₂O on MgO below 573 K (mainly at room temperature) was investigated using TPD, IR and ESR spectroscopies. The effect of UV-irradiation was also studied. In the dark, the partial oxidation reaction did not proceed at room temperature but did when the reaction temperature was raised above 423 K. This temperature coincides well with that of decomposition of N₂O, and O^–₂ seems to be the active oxygen species. However, most of the partial oxidation products, OCH^–₃, are easily oxidized above this temperature to give carbonates. Under UV-irradiation, the partial oxidation reaction of CH₄ by N₂O proceeded at 323 K and gave HCOO^–, OCH^–₃ and C₂–C₇ hydrocarbons. Photodecomposition of N₂O also easily proceeded at 323 K, and O^– was formed at the initial stage. O^– thus formed is an active oxygen species. Hence, it is demonstrated that decomposition of N₂O is a key factor in the reaction of CH₄ with N₂O at low temperatures, either in the dark or under UV-irradiation. Low-coordinated surface ions play no important role in the partial oxidation with N₂O as the oxidant.