Effect of ZrO 2 -doping of nanosized Fe 2 O 3 /MgO system on its structural, surface and catalytic properties Neveen A. Hassan a , Sahar A. El-Molla b, *, Ghada M. Mohamed a , Gehan A. Fagal a a National Research Center, Dokki, Cairo, Egypt b Chemistry Department, Faculty of Education, Ain Shams University, Roxy 11757, Cairo, Egypt 1. Introduction Several parameters may affect the physicochemical, surface and catalytic properties of various catalytic systems toward certain catalytic reaction [1] such as preparation conditions [2], thermal treatment [3], choice of the support material [4] and doping with certain foreign oxides [5]. Supported transition metal oxides are interesting catalysts due to their surface acid–base character [6] and oxidation–reduction properties [7]. Fe 2 O 3 -based catalysts are of significant importance in oxidation processes [8,9] and in technological applications such as integrated microwave devices [10], CO gas sensors and pollution control devices [11]. Most of divalent metal oxides (MO) interact with Fe 2 O 3 yielding the corresponding ferrite (MFe 2 O 4 ) [12]. The enhancement of ferrite formation due to doping with certain foreign oxide had been attributed to formation of ferrites is much influenced by the prehistory of parent oxides, their ratio and doping with certain foreign oxides [12]. The enhancement of ferrite formation due to doping with certain foreign oxide has been attributed to an effective increase in the mobility of the reacting cations [13]. Ferrites are used as catalysts and permanent magnets in microwave devices and digital recording devices of computer [14]. Magnesium oxide with high surface area and nanocrystalline structure has promising applications as a catalyst and catalyst support for some reactions such as dry reforming [15] and oxidative dehydrogenation of butane [16]. Doping of metal oxide system with certain foreign oxides brought about significant modifications in their electrical, optical, magnetic, surface and catalytic properties [5,17]. The acid–base properties of MgO induced by promotion with foreign cations depend on both the amount and the kind of the cation added [18]. El-Molla has reported that ZrO 2 -doping of CuO/MgO system enhanced its catalytic activity in iso-propanol conversion [17] and H 2 O 2 decomposition [19]. ZrO 2 /Cu 2+ has been reported to be an effective catalyst for NO reduction by hydrocarbons in the presence of oxygen [20]. It also exhibits high activity and selectivity for MeOH formation from CO 2 and H 2 [21,22]. Addition of zirconia to cobalt/Al 2 O 3 enhanced its activity and selectivity toward Fisher–Tropsch reaction [23]. The addition of zirconia to catalysts containing cobalt and silica resulted in an excellent activity and selectivity for the production of long chained hydrocarbons, which can be subsequently hydrotreated to give synthetic petroleum, diesel or aviation fuel [24]. The doped catalysts exhibited excellent catalytic activities in oxidation Materials Research Bulletin 47 (2012) 2655–2661 A R T I C L E I N F O Article history: Received 2 October 2011 Received in revised form 9 March 2012 Accepted 17 April 2012 Available online 24 April 2012 Keywords: A. Nanostructures A. Oxides C. X-ray diffraction D. Catalytic properties D. Surface properties A B S T R A C T Fe 2 O 3 /MgO system was prepared by wet impregnation method followed by treatment with different amounts of Zr-dopant salt then heating at 500 and 700 8C. The dopant concentrations were 0.48, 0.95 and 1.4 mol% ZrO 2 . Pure and variously doped solids were characterized using XRD, N 2 -adsorption isotherms carried out at 196 8C and catalytic decomposition of H 2 O 2 in aqueous solution at 25–35 8C. The results revealed that the nanosized MgO phase was only detected in the diffractograms of pure and doped solids calcined at 500 8C. Heating pure and doped solids at 700 8C produced nanosized MgFe 2 O 4 phase together with MgO phase. Pure and ZrO 2 -doped solids calcined at 500 and 700 8C are mesoporous adsorbents. The doping process brought about a measurable decrease in the S BET of Fe 2 O 3 /MgO system with subsequent increase in its catalytic activity. The catalytic activity of the investigated system toward H 2 O 2 decomposition, expressed as reaction rate constant per unit surface area was found to increase as a function of dopant concentration. The maximum increase in the reaction rate constant per unit surface area measured for the reaction carried out at 30 8C attained 125% for the heavily doped samples. This significant increase was based on the catalytic activity of pure catalyst sample measured under the same conditions. ß 2012 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +20 2 24558087/24558086; fax: +20 2 22581243. E-mail address: saharelmolla@yahoo.com (S.A. El-Molla). Contents lists available at SciVerse ScienceDirect Materials Research Bulletin jo u rn al h om ep age: ww w.els evier.c o m/lo c ate/mat res b u 0025-5408/$ – see front matter ß 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.materresbull.2012.04.026