Support effect on complete oxidation of volatile organic compounds over Ru catalysts Tomohiro Mitsui, Kazuki Tsutsui, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi * Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan Received 5 October 2007; received in revised form 26 November 2007; accepted 11 December 2007 Available online 23 December 2007 Abstract Catalytic combustion of ethyl acetate, acetaldehyde, and toluene was investigated on various supported Ru catalysts prepared by the impregnation method, and the effect of reduction treatment on the activity was examined. Among the as-calcined catalysts tested, Ru/CeO 2 showed the highest activity for all tests regardless of the pre-treatment in hydrogen atmosphere. The catalytic activity of Ru/SnO 2 was significantly degraded by the reduction treatment, whereas the activity of Ru/ZrO 2 and Ru/g-Al 2 O 3 was enhanced. To reveal these phenomena, the as-calcined and reduced catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and BET surface area. The dispersion of ruthenium on the supports was evaluated by chemisorption methods of carbon monoxide. The catalytic activity was strongly related to ruthenium species easily oxidizable and reducible at low temperatures. Such ruthenium species were loaded on CeO 2 in a highly dispersed state, resulting in the highest activity. # 2008 Elsevier B.V. All rights reserved. Keywords: Volatile organic compounds; Catalytic combustion; Supported Ru catalysts; Reduction treatment 1. Introduction Volatile organic compounds (VOCs) have relatively high- vapor pressure and thus easily vaporize under ambient conditions. VOCs are known to cause air pollution such as photochemical smog, ground-level ozone, sick house syn- drome, and chemical sensitivity [1–3]. Various methods such as catalytic combustion, flame combustion, catalytic decomposi- tion using ozone and plasma, photocatalytic decomposition, adsorbent-based methods, and so on, have been intensively investigated for effective abatement of VOCs [4–10]. Among these methods, catalytic combustion has advantageous features for VOCs removal: (i) complete combustion of dilute fuel proceeds stably at low temperatures; (ii) extremely low emission of NO x and unburned fuels can be achieved [11]. In general, supported precious metal catalysts exhibit high activity for low-temperature oxidation of VOCs [12–17]. Among supported precious metal catalysts, Ru catalysts are known to be active for various catalytic reactions such as, e.g., water–gas shift reaction, ammonia synthesis, and reduction of NO by hydrocarbon [18–22]. A few studies have been conducted so far on VOC combustion over supported Ru catalysts, despite the various applications in the wide areas as mentioned above. Only wet air oxidation of VOCs has been conventionally carried out over supported Ru catalysts [23–25]. This method, however, needs highly pressurized conditions in order to oxidize VOCs at low temperatures, and is inappropriate for practical use. As an alternative, VOC oxidation in gas phase should be investigated under atmospheric pressure. The aim of this work is to develop catalysts with high- combustion efficiency for VOCs at low temperatures. Several oxides supported ruthenium catalysts (Ru/oxide) were pre- pared, and catalytic oxidation of VOCs such as ethyl acetate, acetaldehyde, and toluene was examined. In addition, the influence of preparation conditions including reduction treatment on the catalytic activity was investigated. 2. Experimental 2.1. Catalyst preparation Supported Ru catalysts were prepared by the impregnation method. The following oxides were selected as support www.elsevier.com/locate/apcatb Available online at www.sciencedirect.com Applied Catalysis B: Environmental 81 (2008) 56–63 * Corresponding author. Tel.: +81 75 383 2519; fax: +81 75 383 2520. E-mail address: eguchi@scl.kyoto-u.ac.jp (K. Eguchi). 0926-3373/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2007.12.006