Chemical Engineering Science 56 (2001) 57}67 Simulation of a membrane reactor for oxidative dehydrogenation of propane, incorporating radial concentration and temperature pro"les K. Hou, R. Hughes*, R. Ramos, M. Mene H ndez, J. Santamarm H a Department of Chemical and Environmental Engineering, Faculty of Science, University of Zaragoza, 50009 Zaragoza, Spain Department of Chemical Engineering, University of Salford, Salford M54WT, UK Received 1 March 2000; received in revised form 7 June 2000; accepted 30 August 2000 Abstract A model for membrane reactors is proposed, taking into account the radial concentration pro"les for each reactant, as well as the temperature pro"les. This model is applicable for a membrane reactor with a "xed bed of catalyst inside the membrane and with distribution of one of the reactants along the reactor through the membrane. The model predictions are compared with the results obtained in an experimental reactor, and the e!ect of an increase in the reactor diameter and other changes in the operation conditions are studied by means of the model.  2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Membrane reactors have been widely studied during the last decade, as may be seen in several reviews (Hsieh, 1991, 1996; Shu, Grandjean, Van Seste, & Kaliaguine, 1991; Zaman & Chakma, 1994; Saracco & Specchia, 1994; Falconer, Noble, & Sperry, 1995; Coronas & Santamarm H a, 1999). Although many possibilities exist, two main kinds of membrane reactor may be identi"ed: (a) the membrane is employed to separate selectively one of the reaction products. This is used to improve the yield in an equilibrium limited reaction, and has been demon- strated for several dehydrogenation reactions, using hydrogen-selective membranes; (b) the membrane is em- ployed to distribute one of the reactants along a catalyst bed. This operation mode has been employed in many oxidation reactions, such as oxidative coupling of methane (Coronas, Menendez, & Santamarm H a, 1994a; Tonkovich, Secker, Reed, Roberts, & Cox, 1995; Ramachandra, Lu, Ma, Moxer, & Dixon, 1996), oxida- tive dehydrogenation of ethane (Coronas, Menendez, & Santamarm H a, 1995a,b; Tonkovich, Zike, Jimenez, Roberts, & Cox, 1996), propane (Pantazidis, Dalmon, & * Corresponding author. Tel.: #44-161-2955081; fax: #44-161- 2955380. E-mail address: r.hughes@chemistry.salford.ac.uk (R. Hughes). Mirodatos, 1995; Ramos, Menendez, & Santamarm H a, 2000) and butane (Te H llez, Menendez, & Santamarm H a, 1997); butane oxidation to maleic anhydride (Qin, Daiqui, & Zhongtao, 1995; Te H llez, Mallada, Menendez, Santamarm H a, & Lombardo, 1996) and has also been pro- posed for methane oxidation to methanol (Chellappa, Fuangfoo, & Viswanath, 1997). In many cases an improvement in yield to the desired product has been obtained, due to the lower oxygen partial pressure, that often improves the selectivity to the desired products and minimises production of CO and CO  . Simultaneously with the experimental studies, several authors have developed mathematical models to predict the behaviour of the reactor by means of simulation. In this way, Santamarm H a, Miro, and Wolf (1991), Santamarm H a, Menendez, Pena, and Barahona (1992) and Reyes et al. (1993a,b) suggested that the distribution of oxygen along several points along the reactor can im- prove the yield to ethane and ethylene in oxidative coup- ling of methane (OCM). Several authors employed a simulation model to show how this system provides improved selectivity in phthalic anhydride production (Papageorgiu & Froment, 1996) and some safety and operational advantages in oxidative dehydrogenation of ethane (Al-Sherehy, Adris, Soliman, & Hughes, 1998). For the latter with a large number of distribution points behaviour similar to that of the membrane reactor is obtained. Cheng and Xhuai (1995) and Kao, Lei, and Lin 0009-2509/01/$ - see front matter  2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 0 9 - 2 5 0 9 ( 0 0 ) 0 0 4 2 2 - X