Hydroxylation of Benzene by Activated Carbon Catalyst

Phenol is widely used in industry. The hydroxylation of benzene to phenol can meet the increasing requirement for phenol and green chemistry. Commercial wood-based activated carbon was treated by different methods, including oxidation by nitric acid and hydrogen peroxide and thermal treatment at different temperatures, and used as the catalyst for the hydroxylation of benzene to phenol in acetonitrile using H2O2 as oxidant. The mechanism of the hydroxylation was also investigated. The activated carbon samples were characterized by Boehm titration, nitrogen adsorption, and X-ray photoelectron spectroscopy. The pH had a significant effect on the phenol yield. The effect of benzene adsorption was also investigated. Several model compounds with oxygen groups were used as catalysts for the hydroxylation of benzene. The reaction between phenolic hydroxyl and quinone on the surface of activated carbon was responsible for the hydroxylation of benzene to phenol when it activated H2O2 to form the hydroxyl radical. Activated carbon was an efficient and stable catalyst and a maximum phenol yield of 14.4% was obtained under the optimal reaction conditions.