Model-Based Analysis of Reactor Feeding Policies for Methane Oxidative Coupling H. R. Godini, †,‡ H. Arellano-Garcia,* ,† M. Omidkhah, ‡ R. Karimzadeh, ‡ and G. Wozny † Chair of Process Dynamics and Operation, Berlin Institute of Technology, Strasse des 17. Juni 135, Sekr. KWT9, 10623 Berlin, Germany, and Chemical Engineering Department, Tarbiat Modares UniVersity, 14155-143, Tehran, Iran In this work, a new feeding policy structure for an alternative operation mode of the packed bed membrane reactor (PBMR) is proposed in order to increase the efficiency of the OCMsoxidatiVe coupling of methanesprocess. This structure has a high potential to improve the process performance in comparison to fixed bed reactors (PFRs) and even to a conventional PBMR design structure. The main drawbacks in operating PFR or PBMR have been to find suitable operation policies toward the enhancement of both yield and selectivity at the same time. In this work, a model-based comparative study of the OCM process performance for these three reactors types is presented. For this purpose, the effect of oxygen accessibility in the different design structures is investigated. Basically, the new proposed feeding policy structure combines the advantages of PFR and the conventional PBMR so as to get a high yield amount by cofeeding methane and oxygen into the reactor entrance while guaranteeing an acceptable level of selectivity by reducing the accessibility to ethylene and oxygen, in particular, at the reactor end. Moreover, using the potential of the proposed operation mode, it is now possible to build a reactor network consisting of the new proposed and the conventional PBMR in order to treat the shell side gas streams, which results from each PBMR structure. The analysis of the proposed reactor network shows a performance of 23.21% yield, 53.93% selectivity, and 42.66% methane conversion, respectively. Besides, a sensitivity analysis is performed in order to analyze the effect of reactant accessibility in the proposed feeding policy structure. The results are analyzed along with the study of the optimal operating range in order to conceptually design a membrane reactor network toward satisfying economical and industrial considerations in terms of selectivity, one-pass yield, and methane conversion. 1. Introduction The OCM (oxidative coupling of methane) process, in which methane is catalytically converted to C 2 products (ethane and ethylene), is considered as a suitable technology with high potential to exploit the huge amounts of natural gas resources. Since the undesired CO 2 production reduces the process efficiency drastically, obtaining simultaneously a high C 2 yield and selectivity still remains as a challenge. To address this issue, in the last two decades, the application of membrane reactors has been proposed. 1-3 In order to decrease the undesired reactions, other researches have also focused on the accessibility control of oxygen as an option. 4-6 In a previous work, 7 the thermodynamic equilibrium displacement was proposed, where some parts of the products are separated during the reaction time. Moreover, different reactor feeding policies have been compared for the OCM process. 8,9 Recently, a new catalytic reactor was introduced and compared in its performance with other reactor structures. 10 The OCM process can basically be represented by the following main reactions, 7 According to the OCM kinetic, the competition between the undesired (CO 2 production) and the desired reactions (C 2 production) can be managed by manipulating the accessibility to the reactants, i.e. oxygen and ethylene. By doing this in an optimal way, the performance and economy of the OCM process can be improved. For this purpose, some conceptual consider- ations have to be taken into account. First, since the reaction in eq 4 is very important, where ethylene is available, the main part of the undesired product CO 2 is produced at the reactor end. Second, the limiting and defining parameter in CO 2 production is the accessibility to the reactants, i.e., oxygen and ethylene. Third, the reaction order with regard to methane for C 2 formation is always higher while the reaction order with respect to oxygen also for C 2 formation is always lower than that for CO 2 formation, respectively. This is reflected on the ratio of methane to oxygen. In addition, in the reactor entrance, where the reaction rates are high, the yield is affected more. However, any effort to control the selectivity is supposed to manage properly the concentration profiles all through the reactor length. Following these considerations, in this work, a new feeding policy structure for an alternative operation mode of the packed bed membrane reactor (PBMR) is proposed. Moreover, the key idea can be implemented either in an individual reactor or in a reactor network including other reactor types. In the following sections, * To whom correspondence should be addressed. E-mail: arellano-garcia@tu-berlin.de. † Berlin Institute of Technology. ‡ Tarbiat Modares University. CH 4 + 1 4 O 2 ⇒ 1 2 C 2 H 6 + 1 2 H 2 O (1) 1 2 C 2 H 6 + 1 4 O 2 ⇒ 1 2 C 2 H 4 + 1 2 H 2 O (2) CH 4 + 2O 2 ⇒ CO 2 + 2H 2 O (3) 1 2 C 2 H 4 + 3 2 O 2 ⇒ CO 2 + H 2 O (4) Ind. Eng. Chem. Res. 2010, 49, 3544–3552 3544 10.1021/ie900182q  2010 American Chemical Society Published on Web 03/23/2010