Phenol by Direct Hydroxylation of Benzene with Nitrous Oxide - Role of Surface Oxygen Species in the Reaction Pathways

摘要

Transient experiments in a Temporal Analysis of Products (TAP) Reactor were performed to elucidate the role of surface oxygen species in the oxidation of benzene to phenol on ZSM-5 type zeolites with nitrous oxide as a selective oxidant. It was shown by puls experiments with nitrous oxide that the mean lifetime of the generated surface oxygen species is between 0.2 s at 500℃ and about 4.2 s at 400℃. Afterwards the surface oxygen species desorb as molecular oxygen into the gas phase where total oxidation will take place if hydrocarbons are present. Dual puls experiments consisting of a nitrous oxide puls followed by a benzene puls allowed studying the reactivity of the surface oxygen species formed during the first puls. The observation of the phenol formation was impeded due to the strong sorption of phenol. Multipulse experiments were necessary to reach a pseudo steady state phenol yield.