Photocatalytic degradation of acetylene over various titanium dioxide-based photocatalysts F. Thevenet a,b , O. Guaı ¨tella b , J.M. Herrmann a , A. Rousseau b , C. Guillard a, * a Laboratoire d’Application de la Chimie a ` l’Environnement, UMR-CNRS 5634, Universite ´ Claude Bernard Lyon-1, 69100 Villeurbanne, France b Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France Received 15 December 2004; received in revised form 23 March 2005; accepted 25 March 2005 Available online 23 May 2005 Abstract The photodegradation of acetylene (C 2 H 2 ) was investigated over various powders or supported titanium dioxide (TiO 2 ) photocatalysts in air into static conditions. It was found that UV-irradiated TiO 2 is effective in order to lead to the complete mineralization of the pollutant containing a triple carbon–carbon bonding without deactivating. No organic intermediates were detected in the gas phase, implying that oxidation mechanisms take place in the adsorbed phase. The efficiency of P25-Degussa and PC500-Millennium photocatalysts were compared; the mixed anatase/rutile P25-Degussa is reported as the most efficient photocatalytical material in our conditions. The topology of the photocatalyst support is reported as a significant parameter in TiO 2 efficiency. Fibre-deposited photocatalysts lead to the highest activity, and the chemical nature of the fibre did not influence the photodegradation. The influence of TiO 2 amonut, silica binder and adsorbing additives such as zeolite, and activated carbon coupled with TiO 2 photocatalyst were investigated. # 2005 Elsevier B.V. All rights reserved. Keywords: Photocatalytic degradation; Gas phase; Acetylene 1. Introduction Heterogeneous photocatalysis is a very promising technique in order to remediate environmental pollution. It has received a major interest during the last ten years because it can totally destruct organic molecules at a low energy cost. The UV irradiation of titanium dioxide (TiO 2 ) leads to the formation of pairs of electrons and holes which are recombined at 99%. The rest of the electrons and holes are used in reduction–oxidation mechanisms, thus leading to the destruction of organic molecules. After water purification [1], the research focused on photocatalytic oxidation of VOCs in the gas phase. Many VOCs are toxic and some are considered to be carcinogenic, mutagenic or teratogenic, as reported by Wilkinson [2]. Moreover, some are implied in the stratospheric ozone layer depletion. The destruction mechanisms of several types of VOCs have already been investigated. Linear or saturated volatile organic compounds, such as hexane [3,4], heptane [5], octane [6] and isobutane [7] can be removed from gas phase by heterogeneous photocatalysis. Oxygenated VOCs, such as alcohols [8–10] or ketones [11–14], can be easily degradated by UV activation of TiO 2 . Most of the alkenes have been studied too, and irradiated TiO 2 is able to lead towards complete mineralization. Simple molecules, such as ethylene [15,16] or 1-butene [17], as well as complex and halogenated molecules like trichloroethylene can be mineralised [18–20]. In 1989, Hisanaga et al. [21] obser- ved that a double carbon–carbon bonding enhances the photodegradation in comparison with a simple bending. D’Hennezel and Ollis [22] noticed in 1997, that the presence of halogenated heteroatoms except the fluorinated ones[23] lead to the formation of oxidative radicals, significantly improving the photodegradation of organic compounds. The photocatalytic degradation of compounds containing aro- matic cycles [24] has been intensively studied. Toluene [25– 27] and benzene [28–30] are the main aromatic molecules www.elsevier.com/locate/apcatb Applied Catalysis B: Environmental 61 (2005) 58–68 * Corresponding author. Tel.: +33 4 72 43 62 15; fax: +33 4 72 44 84 38. E-mail address: chantal.guillard@univ-lyon1.fr (C. Guillard). 0926-3373/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2005.03.015