Short Communication Carbon black and propylene oxidation over Ru/Ce x Zr 1-x O 2 catalysts Doris Homsi a , Samer Aouad a,b,c, ⁎, John El Nakat a , Bilal El Khoury a , Pierre Obeid a , Edmond Abi-Aad b,c , Antoine Aboukaïs b,c a Department of Chemistry, Faculty of Sciences, University of Balamand, P.O. Box 100, Tripoli, Lebanon b Univ Lille Nord de France, F-59000 Lille, France c ULCO, LCE, F-59000 Dunkerque, France abstract article info Article history: Received 23 November 2010 Received in revised form 5 January 2011 Accepted 12 January 2011 Available online xxxx Keywords: Carbon black Catalyst Cerium Oxidation Propylene Ruthenium Zirconium The effect of addition of ruthenium to different Ce x Zr 1-x O 2 (0 ≤ x ≤ 1) supports on the oxidation of propylene and carbon black (CB) was investigated. The results showed that different reactive ruthenium oxide species are formed following calcination at 600 °C. The reactivity increases with the cerium content in the support, Ru/CeO 2 being the most reactive catalyst. However, the Ce 0.5 Zr 0.5 O 2 support and corresponding catalyst, Ru/ Ce 0.5 Zr 0.5 O 2 , exhibited decreased reactivities comparing to solids with lower cerium content. This was ascribed to the formation of a solid structure that inhibits the interaction between cerium and ruthenium oxide species following impregnation. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Several recent legislations concern various types of pollutants and have as a major objective the improvement of air quality. Among these pollutants, volatile organic compounds (VOCs) and particulate matter (PM) have been a major challenge for car manufacturers and researchers. One of the principal solutions to reduce their emissions is the catalytic oxidation technique [1]. In general, supported precious metals such as Pt and Pd are well established as efficient catalysts for VOCs combustion [2]. They are very reactive in the complete oxidation and they avoid the formation of by-products. However, it becomes necessary to optimize the composition of the catalysts in order to obtain new lower cost catalytic materials with low toxicity [3]. The use of cerium oxide (CeO 2 ) as oxidation catalyst has been claimed by different authors. It is widely used as a support because it stores and releases oxygen via the shift between its redox couple Ce 4+ (CeO 2 ) and Ce 3+ (Ce 2 O 3 ) under oxidizing and reducing conditions [4]. Zirconium oxide (ZrO 2 ) is used as a support in many oxidation reactions [5]. In fact, the easiness to exchange oxygen atoms of the tetragonal or cubic ZrO 2 phase makes them suitable for redox catalysis [6]. In addition, ZrO 2 is capable to interact strongly with the metal component and, therefore, to produce an enhancement in the stabilization of metal clusters [5]. On the other hand, ruthenium oxide catalysts showed good reactivity in acetic acid, propene and CO oxidation reactions and in various catalytic reactions such as water– gas shift, ammonia synthesis and reduction of NO [1,7]. Indeed, the association of ruthenium oxide and ceria establishes a successful catalytic system in oxidation reactions [8]. In fact, under oxidative conditions, Ru is transformed to RuO 2 showing highly desirable reactivity and stability and having a lower cost than other noble metals [9]. However, few studies have been devoted to the total oxidation of volatile organic compounds and carbon black in the presence of Ru over CeO 2 and ZrO 2 [10]. In this paper, the oxidation of soot and propylene over Ru/Ce x Zr 1-x O 2 catalysts is investigated. Structural studies are used to correlate the intrinsic properties of the solids to their catalytic performances. 2. Experimental Cerium oxide calcined at 500 °C was prepared by precipitation from cerium (III) nitrate hexahydrate Ce(NO 3 ) 3 .6H 2 O with sodium hydroxide according to [3]. Zirconium oxide calcined at 500 °C was prepared by the precipitation from zirconyl chloride octahydrate ZrOCl 2 .8H 2 O and ammonium hydroxide according to [9]. Ce x Zr 1-x O 2 (0 ≤ x ≤ 1) mixed supports were prepared by coprecipitating ZrOCl 2 .8H 2 O and Ce(NO 3 ) 3 .6H 2 O under the required proportions Catalysis Communications 12 (2011) 776–780 ⁎ Corresponding author at: Department of Chemistry, Faculty of Sciences, University of Balamand, P.O. Box 100, Tripoli, Lebanon. Tel.: +961 6 930250x3908; fax: +961 6 930277. E-mail addresses: dhomsy@balamand.edu.lb (D. Homsi), samer.aouad@balamand.edu.lb (S. Aouad), john.nakat@balamand.edu.lb (J. El Nakat), bilal.elkhoury@balamnd.edu.lb (B. El Khoury), pobeid@balamand.edu.lb (P. Obeid), abiaad@univ-littoral.fr (E. Abi-Aad), aboukais@univ-littoral.fr (A. Aboukaïs). 1566-7367/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2011.01.014 Contents lists available at ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom