Chemical Engineering Science 62 (2007) 5312 – 5316 www.elsevier.com/locate/ces Inﬂuence of the geometry of a monolithic support on the efﬁciency of photocatalyst for air cleaning M. Furman, S. Corbel ∗ , H. Le Gall, O. Zahraa, M. Bouchy Département de Chimie Physique des Réactions, UMR 7630, Nancy-Université, CNRS, ENSIC, 1 rue Grandville, BP20451, 54001 Nancy Cedex, France Received 19 June 2006; received in revised form 25 November 2006; accepted 16 December 2006 Available online 5 January 2007 Abstract The use of stereolithography is well suited for the fabrication of a monolithic photocatalyst for cleaning of air contaminated by volatile organic compounds (VOCs). In this paper we present the inﬂuence of the geometry of the monolith on the reactor’s efﬁciency. Our aim is to develop a model that describes the basic phenomena, which are involved, i.e., light absorption, hydrodynamic and transfer processes and the reaction kinetics. Three different geometries of the monolith reactor have been tested: mixer (M), crossed channels (C), and star geometry (S ). It appears that the geometry has practically no inﬂuence on the external mass transfer rate but has a great inﬂuence on the kinetics of photocatalysis. The model will be used to predict and optimize the photocatalytic behaviour and to scale up the results to an industrial reactor.  2007 Elsevier Ltd. All rights reserved. Keywords: Catalyst support; Chemical reactors; Photochemistry; Monolith; Microreactors 1. Introduction The contamination of air by many volatile organic com- pounds (VOCs) (Avila et al., 1998; Gao et al., 2002) is a prob- lem of public health due to toxic effects on human body even at very low concentration. Outdoors, the pollution is caused by means of transport and by industry (toxic rejects, solvents, etc.). Indoors, the presence of VOCs is due to domestic materials and products (paints, cleaning products, etc.). With the emission of VOCs from household products, “Sick Building Syndrome (SBS)” has appeared. This term refers to the situation in which occupants have troubles such as irritation, stufﬁness and so on, which are speciﬁc of the occupied building. Today, several strategies are developed to minimize the pollu- tion: elimination of pollutant sources, selection of low-emission materials, better ventilation of conﬁned space, adsorption on activated carbon and use of incinerators. Among the techniques proposed for reducing the indoor and outdoor air pollution, photocatalysis is an advanced oxidation process which has the ∗ Corresponding author. Tel.: +33 3 83 17 51 14; fax: +33 3 83 37 81 20. E-mail address: Serge.Corbel@ensic.inpl-nancy.fr (S. Corbel). 0009-2509/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2006.12.045 advantage to degrade many VOCs into carbon dioxide and water (Bouzaza and Laplanche, 2002). Photocatalysis using TiO 2 as catalyst is an efﬁcient advanced oxidation process (Wu et al., 2004) in which the catalyst TiO 2 is deposited on a suitable support and activated by near UV light. The accessibility of the catalytic surface to the photons and reactants must be optimized (Orlov et al., 2004) and the external mass transfer could play a signiﬁcant role, particularly at low ﬂuid ﬂow rate (Dingwang et al., 2001). Besides, the CAD permits us to create quickly several ge- ometries which can be modiﬁed as necessary. Monolithic sup- ports with complex geometry have been made in epoxy resin using a Nd-YAG laser and the stereolithography process and then coated. The experiments have been carried out in a home- made set-up, in order to determine the geometry inﬂuences on the chemical rate, mass transfer and ﬁnally the photocatalytic efﬁciency. The efﬁciency was carried out by estimating the av- erage degradation rate of methanol at different inlet concentra- tions for three geometries. In order to understand the behaviour and the inﬂuence of the geometry on the photocatalytic activ- ity, a model which takes into account the chemical kinetics was proposed. As most photocatalytic reactions take place on the surface of the catalyst, the intrinsic kinetic rate can be given by the model of Langmuir–Hinshelwood.