Improved performance of non-thermal plasma reactor during decomposition of trichloroethylene: Optimization of the reactor geometry and introduction of catalytic electrode M. Magureanu a, * , N.B. Mandache a , V.I. Parvulescu b , Ch. Subrahmanyam c , A. Renken c , L. Kiwi-Minsker c a National Institute for Lasers, Plasma and Radiation Physics, Str. Atomistilor 409, P.O. Box MG-34, 76900 Bucharest-Magurele, Romania b University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, Bd. Regina Elisabeta, 4-12, 030016 Bucharest, Romania c Ecole Polytechnique Fe ´de ´rale de Lausanne (LGRC-EPFL), CH-1015 Lausanne, Switzerland Received 30 December 2006; received in revised form 26 February 2007; accepted 27 February 2007 Available online 3 March 2007 Abstract The decomposition of trichloroethylene (TCE) by non-thermal plasma was investigated in a dielectric barrier discharge (DBD) reactor with a copper rod inner electrode and compared with a plasma-catalytic reactor. The particularity of the plasma-catalytic reactor is the inner electrode made of sintered metal fibers (SMF) coated by transition metal oxides. In order to optimize the geometry of the plasma reactor, the efficiency of TCE removal was compared for different discharge gap lengths in the range of 1–5 mm. Shorter gap lengths (1–3 mm) appear to be more advantageous with respect to TCE conversion. In this case TCE conversion varies between 67% and 100% for input energy densities in the range of 80–480 J/l, while for the 5 mm discharge gap the conversion was lower (53–97%) for similar values of the input energy. As a result of TCE oxidation carbon monoxide and carbon dioxide were detected in the effluent gas. Their selectivity was rather low, in the range 14–24% for CO 2 and 11–23% for CO, and was not influenced by the gap length. Several other chlorinated organic compounds were detected as reaction products. When using MnOx/SMF catalysts as the inner electrode of the DBD reactor, the TCE conversion was significantly enhanced, reaching 95% at 150 J/l input energy. The selectivity to CO 2 showed a major increase as compared to the case without catalysts, reaching 58% for input energies above 550 J/l. # 2007 Elsevier B.V. All rights reserved. Keywords: Non-thermal plasma; Dielectric barrier discharge; Chlorinated volatile organic compounds; Trichloroethylene; Plasma-catalysis 1. Introduction Air pollution by volatile organic compounds (VOC) is an issue of major concern due to both environmental and medical reasons. Non-thermal plasma generated in electrical discharges is attractive for VOC removal from contaminated air streams, since it can be operated at room temperature and atmospheric pressure, over a wide range of gas flow rates and concentrations [1–5]. The energy dissipated in the plasma is mostly used to accelerate the electrons and not spent on heating the entire gas stream, as in thermal or thermo-catalytic processes. The energetic electrons in the plasma are highly efficient in producing radicals and oxidizing agents, which can react with the VOC molecules decomposing them. Various types of electrical discharges have been investigated for the oxidation of chlorinated hydrocarbons: pulsed corona discharges [5–9], atmospheric pressure glow discharges [10], dielectric barrier discharges [8,9,11–16], dielectric packed-bed discharges [3,4,8,12,15,17], surface discharges [13,14,18]. In a recent review of the physics and applications of dielectric barrier discharges (DBD) [2], Kogelschatz addresses also the treatment of VOC, mentioning as main advantages of DBDs their simplicity and scalability. In this work trichloroethylene (C 2 HCl 3 , TCE) was chosen as a model VOC compound. The plasma was generated in a dielectric barrier discharge (DBD) operated in ac mode at www.elsevier.com/locate/apcatb Applied Catalysis B: Environmental 74 (2007) 270–277 * Corresponding author. E-mail address: monimag@infim.ro (M. Magureanu). 0926-3373/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2007.02.019