Co and Ni ferrospinels as catalysts for propane total oxidation Adriana Urda ˘ a , Adrien Herraïz a , Ákos Rédey b , Ioan-Cezar Marcu a, * a Department of Chemical Technology and Catalysis, Faculty of Chemistry, University of Bucharest, 4-12, Blv. Regina Elisabeta, 030018 Bucharest, Romania b Department of Environmental Engineering and Chemical Technology, Faculty of Engineering, University of Pannonia, 10 Egyetem St., H-8201 Veszprém, Hungary article info Article history: Received 19 March 2009 Received in revised form 30 April 2009 Accepted 6 May 2009 Available online 12 May 2009 Keywords: Total oxidation Propane Ferrospinels abstract Co and Ni ferrospinels were prepared by coprecipitation and by mechano-chemical method, character- ized using XRD, N 2 adsorption, EDX and H 2 -TPR techniques and tested in the catalytic total oxidation of propane within the temperature range of 250–600 °C. Depending on the ferrospinel composition, the method of preparing it and the reaction conditions, total conversion to CO 2 was observed at temper- atures between 400 °C and 500 °C. The best results were obtained with the Co ferrite catalyst prepared by coprecipitation, which gives total conversion at temperatures as low as 400 °C. The ferrospinel catalysts showed a good stability during the catalytic test. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction Volatile organic compounds (VOC) emitted during many indus- trial processes and transport activities contribute significantly to the atmospheric pollution, they being associated with the increase in photochemical smog, depletion of stratospheric ozone and the production of ground-level ozone [1]. One of the most effective and economically attractive methods of their neutralization is the catalytic total oxidation to carbon dioxide and water [2]. When large gas volumes have to be treated, catalytic total oxidation has to be performed at very high space velocity requiring a very active catalyst. Alkanes are amongst the most prevalent environmental VOC emissions due to their use as transportation fuels as well as being essential feedstocks for chemicals production. Although al- kane oxidation leads to CO 2 , another greenhouse gas, this can be readily absorbed whereas alkanes cannot. On the other hand, the difficulty in destroying light alkanes by catalytic total oxidation, since they are very difficult to activate, makes them excellent mod- el compounds to test the efficiency of catalysts for VOC combus- tion, as the catalytic combustion of most organic compounds would be ensured if light alkanes are quantitatively abated. Seventy-five percent of the catalysts used for VOC destruction are precious metal catalysts, generally supposed to be more active than metal oxide catalysts [3]. Nevertheless they have some disad- vantages like high sintering rates, volatility, poisoning in presence of water or sulfur compounds and high price [4]. On the other hand, metal oxides have certain advantages, like price, high ther- mal stability, higher resistance to poisoning and the easy way of preparation, and they appear to be a promising solution [5]. More- over, it was recently shown [3] that metal oxides are not necessar- ily less active than noble metals. In recent years, many efforts were directed towards the design of catalytic materials based on simple and mixed transition-metal oxides as a replacement for noble metal catalysts. Nevertheless, to our knowledge, there are no studies investigating Ni and Co ferro- spinels as catalysts for lower alkanes total oxidation but, on the other hand, Co ferrite based catalysts were shown to be effective for the total oxidation of chlorobenzene [6] and Ni ferrite, for CO oxidation [7,8]. In this paper, we present a study of Co and Ni ferrospinels, pre- pared by coprecipitation or by mechano-chemical method, used for the first time as catalysts for total oxidation of propane. 2. Experimental 2.1. Catalysts preparation Two types of methods have been used to prepare the catalysts. The first one (M1) has been applied to the synthesis of both Ni and Co ferrites. It was based by the coprecipitation of metal hydroxides from a stoichiometric mixture of 1 M solution of ferric nitrate and 1 M solution of other nitrates, using 1 M solution of sodium hydroxide as the precipitating agent. The pH of the final slurry was carefully adjusted to 10. The precipitate was kept 72 h in its mother liquor under stirring for ageing with the aim of obtaining a more organized material, and washed free of nitrate ion and alka- li. It was then filtered, dried at 60 °C for 72 h and at 80 °C, 100 °C and 120 °C for 1 h at each temperature and calcined at 200 °C, 1566-7367/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2009.05.002 * Corresponding author. Tel.: +40 214103178; fax: +40 213159249. E-mail addresses: marcu.ioan@unibuc.ro, ioancezar_marcu@yahoo.com (I.-C. Marcu). Catalysis Communications 10 (2009) 1651–1655 Contents lists available at ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom