Available online at www.sciencedirect.com Science Direct Catalysis Communications 8 (2007) )50-156 CATALYSIS COMMUNICATIONS www.clsevier.corn/locate/catcom Vanadia supported on ceria: Characterization and activity in liquid-phase oxidation of ethylbenzene T. Radhika, S. Sugunan * Dcpurtmcnt of Applied Chemistry. Cochin University of Science and Technology, Cochin-Tl, Kerala 682022, India Received 8 March 2006; received in revised form 8 May 2006; accepted 23 May 2006 Available online 3 June 2006 ties of ceria (Ce 4 + /Ce H ) and the high lability of its lattice oxygen are among the most important factors that contrib- ute to the catalytic reactivity in oxidation reactions [IOJ. Side-chain oxidation of alkyl aromatics using cleaner peroxide oxidants catalyzed by heterogeneous catalysts has been much interesting [11 J, Effective utilization of eth- ylbcnzene, available in the xylene stream of the petrochem- ical industry to more value added products is a promising one in chemical industry. The oxidation products of ethyl- benzene are widely employed as intermediates in organic, steroid and resin synthesis [12-14]. Zeolite encapsulated Cot llj, Ni(ll) and Cu(Il) complexes gave acetophenone as the only partial oxidation product during ethyl benzene oxidation with H 20 2 [15]. Titanosilicates mainly catalyze ring hydroxylation of arenes with H 20 2 , whereas vanadium and chromium substituted zeolites and aluminophosphate molecular sieves have been known to favour side-chain oxi- dation selectively [16]. In the present work. we report the structural character- ization of ceria supported vanadia catalysts for various loading of V205 observed using different physico-chemical 1- , author. Tel.: +91 4842575804: fax: +9\ 484 2577595. E-mail adiln.s.\"_ssg@cusat.ac.in (S. Sugunanj. I 1. Introduction ! Supported vanadium oxide catalysts have been exten- I ".:jy used for catalyzing several oxidation reactions [1- 5J..The redox chemistry of ceria is a critical parameter in I u:::""\ffieiency of multifunctional components of three-way automotive catalysts and applications of these materials I other catalytic processes such as oxygen perme- ation membrane systems. deNO, catalysis, oxidation of I ... and catalytic wet oxidation are being extensively studied (6,7J. In recent years vanadia/ceria combination ,",-='ysts have been the subjects of numerous investigations I because of its wide range applications in catalysis and •• science [8,9]. Generally, oxidation rate is limited I by the oxygen transfer from the liquid phase to the metal ,..":'e sites. while ceria is able to enhance this oxygen trans- I fer to efficiently catalyze the reactions. The redox proper- .:) ...,.., Abstract I ,'"""'I ""anildia/ceriil catalysts (2 iO wt':;', of V20 5) were prepared by wet impregnation of ammonium mctavanadate in oxalic acid solution. 'StJilIl,ctural characterization was done with energy dispersive X-ray analysis (EDX). powder X-ray diffraction (XRD), BET surface area I FT-IR spectroscopy and nuclear magnetic spectral analysis ( 51V MASNMR). XRD and 5lV MASNMR results show I dispersed vanadia species at lower loadings and the formation of CeV0 4 phase at higher V 20S loading. The catalytic activity I o..:1talysts was conducted in liquid phase oxidation of ethylbenzenc with H 20 2 as oxidant. The oxidation activity is increased with load- ing up to 8 wt% V205 and then decreased with further increase in V205 content to 10 wt%. Different vanadia species evidenced by various , were found to be selective towards ethylbenzene oxidation. The CeV0 4 formation associated with increased concentration of I vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone. Elsevier B.V. All rights reserved. Vanadia: Ceria: CeVO.; Ethylbenzenc oxidation: SIV MASNMR 1- 1566-7367/5 - see front matter © 2006 Elsevier B.V. All rights reserved.