Chemical Engineering Journal 166 (2011) 218–223 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej MnO x supported on metallic monoliths for the combustion of volatile organic compounds Fabiola N. Aguero a,∗ , Bibiana P. Barbero a , Luciano Costa Almeida b , Mario Montes b , Luis E. Cadús a a Instituto de Investigaciones en Tecnología Química (INTEQUI), Universidad Nacional de San Luis (UNSL)–Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Casilla de correo 290, 5700 San Luis, Argentina b Grupo de Ingeniería Química, Dt. de Química Aplicada, Fac. de Química de San Sebastián, Universidad del País Vasco. P. Manuel de Lordizabal, 3, 20009 San Sebastián, Spain article info Article history: Received 29 April 2010 Received in revised form 22 October 2010 Accepted 26 October 2010 Keywords: Manganese oxide Ferritic alloys VOC Total oxidation abstract The most convenient way to prepare structured manganese oxide catalyst for the combustion of volatile organic compounds was studied. The preparation conditions (solid concentration in the slurry, the addi- tion of a suspension stabilizer, and the immersion numbers) were studied. The catalytic properties of these catalysts were evaluated in ethanol, ethyl acetate and toluene combustion. The surface area and the catalytic activity of monoliths in VOCs combustion increased with the amount of catalyst retained. A higher catalyst loading and a more homogeneous and well adhered layer was obtained using a 30 wt% solid content suspension and performing two immersions. The addition of Nyacol ® is not necessary to improve the stability of suspensions because these are stable by themselves. The washcoating of mono- liths with a –-Al 2 O 3 suspended in manganese acetate solution not only reduces the number of stages during the preparation procedure but also produces more active catalysts. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The control of VOCs emissions is often carried out by thermal incineration (at temperatures higher than 1200 K) or adsorption, but catalytic oxidation is a promising abatement technology for VOCs, since it can be carried out at lower temperatures (below 800 K), allowing energy saving and promoting the removal of the pollutant by forming harmless products such as H 2 O and CO 2 [1,2]. The most commonly used catalysts in the oxidation of VOC are based on supported noble metals, generally Pt and Pd. However, transition metal oxides, mainly of Co, Cu, Ni and Mn [3] have demonstrated a very good catalytic activity in oxidation reactions and have the additional advantage of having lower cost and greater resistance to deactivation by poisoning [4]. MnO x based materials are among the most interesting catalysts used in catalytic oxidation reactions. These catalysts have been identified as active phases in various processes, as in total oxidation of methane [5], oxidation of CO [6] and various hydrocarbons [7–9]. They are also considered environmental-friendly materials [10]. When large volumes of gas with low concentrations of VOCs must be treated, it is necessary to deposit the active phase on struc- tured supports to ensure the passage of fluids with low pressure drops. The structured supports most widely used are monoliths formed by longitudinal parallel channels. The monoliths can be ∗ Corresponding author. Tel.: +54 2652 426711; fax: +54 2652 426711. E-mail address: fnaguero@unsl.edu.ar (F.N. Aguero). made of ceramic or metallic materials. The most habitual because of its widespread use in the automobile sector are ceramics, mainly cordierite [11], however they have certain limitations related to the minimum wall thickness for a proper extrusion and a low ther- mal conductivity [12]. Although metal monoliths have a higher cost than ceramics ones, they have a higher mechanical strength and thermal conductivity, and also have thinner walls allowing higher cell densities and lower pressure drops. The main disad- vantage is the low adhesion of the coating that acts as support of the active phase. Nowadays, this is overcome by chemical modi- fication in the preparation of the coating and the use of metals or alloys physicochemical and/or thermally treated. Those treatments allow the formation of an adherent and stable oxide layer that anchors the catalytic coating [13]. Ferritic alloys containing Al (such as FeCrAlloy ® ) are used in the fabrication of metallic monoliths because they support high temperatures. Besides, under oxidizing conditions at high temperatures aluminum segregates to the sur- face as an alumina layer in form of whiskers. Such a layer has an adequate roughness to hold the catalytic coating. In a previous work [14] we have reported that supported manganese oxide catalysts showed a good catalytic performance in VOCs oxidation reactions. In particular, the catalyst prepared from manganese acetate as precursor and a –-Al 2 O 3 as support, resulted the most active one in ethanol combustion. The aim of this work is to study the most convenient way to prepare structured manganese oxide catalyst for the combustion of volatile organic compounds. The preparation conditions (solid concentration in the slurry, the addition of a suspension stabi- 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.10.064