2011 Chinese Journal of Catalysis Vol. 32 No. 2 Article ID: 0253-9837(2011)02-0258-06 DOI: 10.1016/S1872-2067(10)60173-8 Article: 258–263 Received 25 September 2010. Accepted 2 November 2010. *Corresponding author. Tel: +98-21-61112614; Fax: +98-21-61113301; E-mail: abadiei@khayam.ut.ac.ir Foundation item: Supported by the University of Tehran. English edition available online at ScienceDirect (http://www.sciencedirect.com/science/journal/18722067). Direct Hydroxylation of Benzene to Phenol over Fe 3 O 4 Supported on Nanoporous Carbon Pezhman ARAB 1 , Alireza BADIEI 1,* , Amir KOOLIVAND 1 , Ghodsi MOHAMMADI ZIARANI 2 1 School of Chemistry, College of Science, University of Tehran, Tehran, Iran 2 Department of Chemistry, Faculty of Science, Alzahra University, Iran Abstract: Fe 3 O 4 /CMK-3 was prepared by impregnation and used as a catalyst for the direct hydroxylation of benzene to phenol with hydro- gen peroxide. The iron species in the prepared catalyst was Fe 3 O 4 because of the partial reduction of iron(III) to iron(II) on the surface of CMK-3. The high catalytic activity of the catalyst arises from the formation of Fe 3 O 4 on the surface of CMK-3 and the high selectivity for phenol is attributed to the consumption of excess hydroxyl radicals by CMK-3. The effect of temperature, reaction time, volume of H 2 O 2 , and amount of catalyst on the catalytic performance of the prepared catalyst were investigated. Under optimized conditions, the catalyst showed excellent catalytic performance for the hydroxylation of benzene to phenol and 18% benzene conversion was achieved with 92% selectivity for phenol and with a TOF value of 8.7 h −1 . The stability of catalyst was investigated by determining its activity after the fourth run and it was found to have decreased to 80% of the fresh catalyst’s activity. Key words: nanoporous carbon; ferroferric oxide; hydroxylation of benzene; phenol CLC number: O643 Document code: A Phenol is one of the most valuable intermediates for manufacturers and it is still being produced by the cumene process. However, the reaction pathway is a multistep proc- ess and it is environmentally unfriendly. In addition, the production of phenol by the cumene process depends on the market price of acetone, which is a by-product of this pro- cedure. These disadvantages limit the efficiency and profit- ability of this process. Therefore, plenty of research has been devoted to realizing an economical and environmen- tally friendly process for the conversion of benzene to phe- nol [1,2]. However, the oxidation of benzene to phenol is challenging because the benzene ring is chemically stable and the oxidation of phenol is much easier than the oxida- tion of benzene [3]. Recently, much effort has been devoted to finding a suitable catalyst for the selective oxidation of benzene to phenol under mild conditions with clean oxi- dants such as O 2 and H 2 O 2 [4−16]. Various supported metal oxides have been studied for the one-step oxidation of ben- zene to phenol using hydrogen peroxide but the self-decomposition of hydrogen peroxide in these reactions has limited its application [17]. The excellent dispersion of metal ions on high surface-area supports can overcome this disadvantage [17]. As a result, porous materials have been extensively used as supports for the conversion of benzene to phenol because of their high surface areas and large pore volumes, which results in the high dispersion of metal ions [18−21]. Because of the relatively low cost of iron salts, suitable iron-containing catalysts for the hydroxylation of benzene to phenol have been sought [22−24]. The catalytic performance of Fe 2 O 3 -containing and Fe 3 O 4 -containing catalysts in the hydroxylation of benzene to phenol has been investigated [22,25]. The use of Fe 2 O 3 -containing catalysts results in a low benzene conversion as well as a low selec- tivity for phenol. Although the catalytic performance of Fe 3 O 4 -containing catalysts is higher than that of Fe 2 O 3 -containing catalysts, the application of Fe 3 O 4 -containing catalysts have been limited because of the difficulty in preventing the further oxidation of phenol in these systems [25]. Therefore, overcoming the disadvan- tages of Fe 3 O 4 -containing catalysts is an interesting chal- lenge for the hydroxylation of benzene to phenol. Choi et al. [18] investigated the catalytic performance of transition metals supported on activated carbon and MCM-41 for the hydroxylation of benzene to phenol. They reported that the hydrophobic nature of activated carbon enhances the cata- lytic performance of transition metals during the hydroxyla- tion of benzene to phenol. Considering the above factors, we prepared an efficient catalyst by loading Fe 3 O 4 onto the surface of CMK-3, which is a highly ordered nanoporous carbon and investigated its catalytic performance for the hydroxylation of benzene to phenol using hydrogen peroxide.