Applied Catalysis A: General 265 (2004) 103–113 Oxidative dehydrogenation of propane on V 2 O 5 /Al 2 O 3 and V 2 O 5 /TiO 2 catalysts: understanding the effect of support by parameter estimation Kamalakanta Routray, K.R.S.K. Reddy, Goutam Deo ∗ Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016, India Received 11 August 2003; received in revised form 29 December 2003; accepted 13 January 2004 Available online 27 February 2004 Abstract In this paper, the effect of the oxide support for supporting the vanadium oxide phase is studied by estimating the reaction parameters for the oxidative dehydrogenation of propane. To achieve this objective, several V 2 O 5 /Al 2 O 3 and V 2 O 5 /TiO 2 catalysts were synthesized by an incipient-wetness-impregnation technique. The supported vanadium oxide catalysts were characterized and the surface area, monolayer coverage and reducibility were determined. The surface area of the catalyst samples was not significantly affected with supported vanadium oxide loading. It was observed that the catalysts contain only molecularly dispersed vanadium oxide species below monolayer coverage, and molecularly dispersed and crystalline V 2 O 5 above monolayer coverage. TPR studies revealed that the V 2 O 5 /Al 2 O 3 samples were more difficult to reduce relative to the V 2 O 5 /TiO 2 samples. The monolayer or near-monolayer catalysts, 10% V 2 O 5 /Al 2 O 3 and 4% V 2 O 5 /TiO 2 , were selected for detailed kinetic analysis. A Mars–van Krevelen (MVK) model containing eight parameters was chosen for this purpose. The parameters were estimated using a genetic algorithm (GA), which optimizes a suitable objective function for a non-linear multi-response system. From the parameters estimated, it was determined that a similar catalytic cycle occurs independent of the oxide support. However, the rate at which the catalytic cycle occurs appears to be much faster on the more reducible titania support compared to the rate on the less reducible alumina support. The degree of reduction varies along the length of the reactor and depends on the support. Thus, the support has a significant effect on the reaction parameters for the oxidative dehydrogenation of propane over supported vanadium oxide catalysts. © 2004 Elsevier B.V. All rights reserved. Keywords: Oxidative dehydrogenation; Propane; Vanadium oxide; Alumina; Titania; Support; Reaction kinetics; Mars–van Krevelen; Genetic algorithm; Kinetic parameters 1. Introduction Supported vanadium oxide catalysts are frequently used as catalysts in partial oxidation reactions [1–4]. In these cata- lysts, Al 2 O 3 , TiO 2 , SiO 2 and ZrO 2 are commonly used as the supports. In comparison with bulk V 2 O 5 , supported vana- dium oxide catalysts show a different behavior in oxidation reactions [5]. Bulk oxides in general cannot be used in in- dustrial processes as they impart poor thermal stability and, mechanical strength and lead to fast deactivation of the cat- alyst. Furthermore, it is also known that bulk V 2 O 5 leads to high combustion of organic molecules to carbon oxides [6]. Several examples of vanadium oxide supported on Al 2 O 3 , TiO 2 , ZrO 2 and SiO 2 supports exist for the oxidative dehy- drogenation (ODH) of propane (C 3 H 8 ) [7–10]. The activity ∗ Corresponding author. Tel.: +91-512-2597881; fax: +91-512-2590104. E-mail address: goutam@iitk.ac.in (G. Deo). and selectivity of these reactions are observed to depend on vanadium oxide loading and on the specific oxide support. Lemonidou et al. [11] studied the ODH of propane reac- tion over vanadium supported on different supports: MgO, Al 2 O 3 , TiO 2 and ZrO 2 , and observed that the activity (moles of propane converted per gram of catalyst) is significantly affected by the support. It follows the order: V 2 O 5 /TiO 2 > V 2 O 5 /ZrO 2 > V 2 O 5 /Al 2 O 3 > V 2 O 5 /MgO. Similar trends in activity as a function of oxide support were observed by Arena et al. [12] and Matra et al. [13]. The propene selec- tivity, however, follows a different trend V 2 O 5 /Al 2 O 3 > V 2 O 5 /ZrO 2 > V 2 O 5 /MgO > V 2 O 5 /TiO 2 . Matra et al. [13] investigated the surface properties of different supported vanadium oxide catalysts by various characterization tech- niques. It was suggested that the surface vanadium oxide species were dispersed on the surfaces of Al 2 O 3 , zeolite and MgO, whereas on TiO 2 they are found to be assem- bled in a layer almost completely covering the support. Fur- thermore, these researchers also observed the presence of 0926-860X/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2004.01.006