Oxidative dehydrogenation of propane over supported chromium–molybdenum oxides catalysts B.Y. Jibril a, * , S.M. Al-Zahrani a , A.E. Abasaeed a , R. Hughes b a Chemical Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia b Chemical Engineering Unit, University of Salford, Maxwell Building, The Crescent, Salford, Manchester M5 4WT, UK Accepted 21 July 2003 Published online: 3 October 2003 Abstract Catalytic oxidative dehydrogenation of propane to propylene was studied on alumina-supported chromium– molybdenum oxides catalysts – 10 wt% Cr x Mo ð1xÞ =c-Al 2 O 3 (where x ¼ 0–1). The catalysts are active for the reaction. Increase in the amount of molybdenum in the catalysts decreases the reducibility and changes the nature of the lattice oxygen in the catalyst as indicated by TPR and XPS data. The catalysts with lower reducibilities exhibits corresponding increase in the propylene selectivities. Alkali metals (Li, K, Cs)-doped 10 wt% Cr 0:8 Mo 0:2 (alkali/CrMo weight ratio of 0–0.175), shows maxima in both propane degrees of conversion and propylene yields in the ratio ranges explored. One of the catalysts (Cs/CrMo ¼ 0.125) exhibits propane conversion of 15.1% and selectivity to propylene of 64.5% at 420 °C. This is among the most promising catalysts reported for oxidative dehydrogenation of propane. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Oxidative dehydrogenation; Propane; Propylene; Chromium oxides; Molybdenum oxides; Alkali metals promoters 1. Introduction The increasing demand of propylene in the in- ternational market and the general tendency of the petrochemical industry to transform cheap and abundant alkanes into more valuable products have spurred research interest in oxidative dehy- drogenation of propane to propylene [1]. This drive is likely to continue since worldwide pro- pylene demand is expected to grow by 5.7% over the next several years with the strongest demand from polypropylene, which has the highest growth rate among polymers [2]. Designing a catalytic system that has high alkenes yield remains a challenging task. Based on this, propane oxidative dehydrogenation (POD) has received extensive research efforts that led to the discovery of several promising catalysts [1]. The most studied catalysts are based on vanadium [3,4], metal tungstates [5], metal molybdates [6] and metal phosphates [7,8]. Keggin-type polyoxotungstate was also reported to be active for the reaction [9,10]. Recently, rare earth vanadates have been reported to have better Catalysis Communications 4 (2003) 579–584 www.elsevier.com/locate/catcom * Corresponding author. Tel.: +966-1467-6897; fax: +966- 1467-8770. E-mail address: baba@ksu.edu.sa (B.Y. Jibril). 1566-7367/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2003.07.001