Liquid-phase oxidation of p-xylene using N-hydroxyimides

In this communication, we describe p-xylene oxidation with molecular oxygen at 373 K and atmospheric pressure using N-hydroxyimide catalysts. p-Xylene conversion was rather high over the first 2 h of reaction and complete by the end of the experiment. The product distribution curves versus reaction time are typical of consecutive reactions. The main intermediate product is p-toluic acid. Peak concentration and the shape of its concentration profile depend heavily on the N-hydroxyimide catalyst used. This effect seems to be related to the NO–H bond dissociation energy (BDE) of the N-hydroxyimides employed.

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► p-Xylene oxidation under mild reaction conditions leads to a high yield of terephthalic acid.
► The key parameter controlling the reactivity of N-hydroxyimides is the bond dissociation energy (BDE) of NO–H.
► A combination of cobalt and manganese salts and N-hydroxysuccinimide is the best catalytic system in the p-xylene oxidation to terephthalic acid.