The enhancement effects of added methanol on methane-selective oxidation in the gas phase reaction of CH4–O2–NO2

Abstract

The reactivity of the selective oxidation of methane in the gas phase reaction of CH₄–O₂–NO₂ was enhanced by the addition of a small amount of methanol. The selectivity of methanol produced at the same level of methane conversion was enhanced by adding a small amount of methanol in the feed gas. The enhanced effect of methanol addition was restricted to methane conversion in the presence of NO₂. The enhancement effect was obtained more effectively when the ratio of methanol to NO₂ was near to 1, at which higher concentration of both methanol and NO₂ a significant enhancement was shown. Theoretical calculations concluded as follows: CH₃OH + NO₂→CH₂OH + HNO₂ was the predominant step of hydrogen abstraction from methanol. HO₂ was then produced by CH₂OH + O₂→CH₂O + HO₂. CH₄ + HO₂→CH₃ + H₂O₂ was the key reaction to enhance the reactivity of methane. HO₂ + OH→H₂O + O₂ brought about an OH radical dissipation reaction to stabilize the produced methanol from the following decomposition reaction: CH₃OH + OH→CH₂OH + HO₂ .