The activation of heterogeneous Fenton-type catalyst Fe-MFI E.V. Parkhomchuk (Kuznetsova) a, * , M.P. Vanina a , S. Preis b a Boreskov Institute of Catalysis, Lavrentiev Avenue 5, Novosibirsk 630090, Russia b Lappeenranta University of Technology, Skinnarilankatu 34, Lappeenranta 53850, Finland Received 2 April 2007; received in revised form 8 July 2007; accepted 15 July 2007 Available online 19 July 2007 Abstract The activation of iron-containing zeolite of MFI structure with mineral and carboxylic acids in heterogeneous Fenton reaction was experimentally studied. The catalytic activity of the zeolite was tested in the hydrogen peroxide decomposition reaction. The activation effect of acids was observed in the following decreasing order: oxalic > acetic > hydrochloric > formic. The catalyst pre-treatment with nitric acid was ineffective. Optimum conditions for the most effective pre-treatment of the zeolite with aqueous oxalic acid solutions were established. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Hydrogen peroxide; Fenton; Heterogeneous catalysis; MFI; Zeolite activation 1. Introduction Zeolites containing transition metal ions have been shown to be promising heterogeneous solid-phase catalysts in oxidation of a series of organic water pollutants with hydrogen peroxide. Such substrates as phenol [1–8], 4- nitrophenol [9], chlorinated phenol [10], carboxylic acids [11–13], 2,4-xylidine [14] and some textile dyes [15–17] were successfully oxidized in heterogeneous Fenton or photo- Fenton reactions. The majority of these studies dealt with the use of the zeolites of MFI structure [1–3,6,9,11,13,18– 21], which showed a higher catalytic activity in a wider pH range as compared to the homogeneous Fenton oxida- tion. The stability and the heterogeneous character of the zeolite catalysts were proved in their manifold consecutive catalytic experiments showing negligible contribution of homogeneous catalysis of leached iron ions [18]. The activation effect of some organic and inorganic acids on Fe-containing MFI-zeolite was studied here: the effect of the acid concentration, treatment time and temper- ature were established. 2. Experimental The experiments were carried out with two catalysts, synthetic and commercial. The synthetic Fe-containing zeolite was produced hydrothermally from silica and sodium hydroxide in the presence of ferric nitrate, using tetrapropylammonium bromide (TPA-Br) as an organic template. 1,1-Dimethylhydrazine, also known as unsym- metrical dimethylhydrazine (UDMH) and ethanol were chosen as aqueous pollutants for the catalyst testing. The molar ratio in the SiO 2 :Na 2 O:TPA-Br:H 2 O:Fe 2 O 3 mixture was chosen as 1:0.1:0.11:25:0.014, respectively. The mixture was placed to a Teflon-coated stainless steel autoclave and kept at 150 °C for 3 days. The obtained crystals were fil- tered, rinsed with distilled water and dried in air. The commercial Fe-containing MFI-zeolite catalyst was obtained from Su ¨ b-Chemie AG (Mu ¨nchen, Germany) known as Fe/H-MFI 25. The XRD analysis was performed by HZG-4 with Cu-Ka radiation in the angle range 2h from 5 to 50°. The XRD spectra of the synthetic and commercial zeolites are shown in Fig. 1. All samples were found to be of 1566-7367/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2007.07.009 * Corresponding author. Tel./fax: +73833331617. E-mail address: ekaterina@catalysis.ru (E.V. Parkhomchuk (Kuznet- sova)). www.elsevier.com/locate/catcom Available online at www.sciencedirect.com Catalysis Communications 9 (2008) 381–385