Journal of Molecular Catalysis A: Chemical 348 (2011) 14–19 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical jou rn al h om epa ge: www.elsevier.com/locate/molcata Liquid phase hydroxylation of benzene to phenol over vanadium substituted Keggin anion supported on amine functionalized SBA-15 Ali Nemati Kharat ∗ , Sayedreza Moosavikia, Bahareh Tamaddoni Jahromi, Alireza Badiei School of chemistry, University College of science, University of Tehran, P.O. Box 13145-1357, Tehran, Iran a r t i c l e i n f o Article history: Received 29 January 2011 Received in revised form 24 July 2011 Accepted 26 July 2011 Available online 4 August 2011 Keywords: Modified SBA-15 Molybdovanadophosphoric acid Hydroxylation Phenol Benzene oxidation a b s t r a c t The Keggin type vanadium substituted molybdophosphoric acid (H 5 PMo 10 V 2 O 40 ) supported on amine functionalized SBA-15 was tested in direct hydroxylation of benzene to phenol in the liquid phase. The catalyst was characterized by various techniques such as X-ray diffraction, FT-IR spectroscopy, thermogravimetric analysis (TGA), N 2 absorption–desorption surface area measurement and SEM. Gas chromatography of products showed high catalytic activity and selectivity to phenol. As we expected, the leaching of heteropoly acid from support during the reaction was negligible, because of strong interaction between heteropoly acid and amine groups of surface. The influence of reaction temperature, reaction time, amount of catalyst and H 2 O 2 were investigated. Under optimized conditions 20% conversion of benzene and 95% selectivity to phenol was achieved. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Phenol is one of the most useful intermediates in manufac- ture of petrochemical, agrochemical and plastics [1–3]. It is also an essential chemical to produce phenolic resins and bisphenol A [4]. Currently, phenol is chiefly produced by three step Huck process that suffers from many disadvantages such as low yield, high energy consumption and production of acetone as byprod- uct [5]. In two past decades many endeavors were carried out to find one step procedure for the production of phenol by direct hydroxylation of benzene in liquid or gas phase. Owing to envi- ronmental and economical aspects, the use of molecular oxygen and hydrogen peroxide is preferred to other oxidants [6,7]. Hydro- gen peroxide in comparison with oxygen shows more activity and better selectivity. In spite of its advantages, hydrogen peroxide is inherently corrosive and tends to catalytic decomposition in high concentration. In order to overcome these significant draw- backs usually diluted aqueous solution is used, however the excess water often produces a biphasic mixture and leads to separation of organic substrate and active catalyst species [8,9]. It is worth mentioning that the reaction of hydrogen peroxide with aromatic compounds proceeds in the presence of transition metal ions of dif- ferent oxidation states [10,11]. Polyoxometalates belong to a large class of nano-sized metal–oxygen clusters. Generally there are two kind of polyoxometalates based on their chemical composition: ∗ Corresponding author. Tel.: +98 21 61112499; fax: +98 21 66495291. E-mail address: alnema@khayam.ut.ac.ir (A. Nemati Kharat). heteropoly and isopoly anions that the former is more active for cat- alytic applications [12]. Molybdenum (VI) and tungsten (VI) are the best polyoxometalates formers as the result of their favorable com- bination of ionic radius, charge and accessibility of empty d orbitals for metal–oxygen  bonding [13]. Heteropoly compounds with their redox and acidic properties are active catalysts for various oxidation reactions [14–17]. In addition, heteropoly compounds have inherent stability toward oxygen donors such as molecular oxygen and hydrogen peroxide, therefore they are useful catalysts for liquid phase oxidation [18]. The main drawback for heteropoly anions catalytic application is their low specific area, hence for many applications, heteropoly compounds are dispersed on a high surface area carriers [19,20]. The result of direct dispersion of HPAs on a conventional supports such as silica, TiO 2 , carbon, or Al 2 O 3 show that anchoring HPA on the surface of these supports is not stable and the loaded HPAs can be easily released by polar sol- vents resulting in the leaching of the active site from the supports. To minimize this problem, modification by silanization has been explored to bind heteropoly acids on the surface of support and an acid–base interaction made has been invoked to explain their interaction [21]. Here, in this work we synthesized the vanadium-substituted heteropoly acid (H 5 PMo 10 V 2 O 40 ·nH 2 O) and loaded this HPA on amine functionalized SBA-15. This catalyst was tested in direct hydroxylation of benzene to phenol and the optimum conditions were investigated. In order to show the influence of silanization, the activity of this catalyst was compared with loaded HPAs according to impregnation method over conventional supports such as NaY and MCM-41. 1381-1169/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2011.07.014