Journal of Natural Gas Chemistry 20(2011)325–333 A simple kinetic model for oxidative coupling of methane over La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ nanocatalyst Ali Farsi 1,2∗ , Sattar Ghader 1 , Ali Moradi 1 , Seyed Soheil Mansouri 1,2 , Vahid Shadravan 1,2 1. Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran; 2. Young Researchers Society, Shahid Bahonar University of Kerman, Kerman, Iran [ Manuscript received September 7, 2010; revised January 19, 2011 ] Abstract A simplified kinetic model for the oxidative coupling of methane over a La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ nanocatalyst is presented. The kinetic model was developed by experimental data in a catalytic micro-reactor covering a wide range of reaction conditions (0.04<P O 2 <0.15 atm, 0.2<P CH 4 <0.85 atm, 800<T <900 ◦ C). Power law rate expressions were used for all reactions. The reaction scheme proposed in this work includes the most important reactions of oxidative coupling of methane and those involved in most of the available mechanisms in the literature. From the experimental data, kinetic parameters, i.e., pre-exponential factors, activation energies and power law exponents, were estimated. The compatibility of model results with experimental data was investigated and the accuracy of the model prediction was evaluated. Rates of methane consumption, C 2+ and CO x formation, methane conversion, and C 2+ selectivity and yield were compared with experimental data using presented kinetics. The kinetic model was also compared with four previous kinetic models in terms of methane conversion. Key words nanocatalyst; kinetic model; oxidative coupling of methane 1. Introduction Oxidative coupling of methane (OCM) is an important process for the catalytic conversion of natural gas [1-3]. Sig- nificant progresses have been made in the last century to im- prove the catalytic performance and to understand the mecha- nism of OCM. However, the low yield of ethylene makes this process far away from the industrial application [4-7]. The kinetics of OCM reaction which produces C 2+ hy- drocarbons (ethane and ethylene) has been studied extensively based on various reaction mechanisms. Former researches have shown that the kinetics of OCM reaction is very compli- cated in terms of the proposed mechanisms since they involve several chemical species [7-13]. Kinetics and mechanisms of the OCM have been classified to: (A) Spectroscopic studies of O - species and the reaction with methane; (B) Kinetic simulations of gaseous phase reactions; (C) Simultaneous kinetic simulation of gaseous phase and surface reactions; (D) Integrating kinetics of many radical reactions of sin- gle or several reactions; (E) Focusing on surface kinetics of methane consump- tion; (F) Power rate law expression of C 2+ (ethane and ethy- lene) and CO x (CO and CO 2 ) formation. Many reaction kinetic expressions have been given in the literature considering these mechanisms such as those pro- posed by Stansch et al. [8], Cheng and Shuai [14], Yaghobi and Ghoreishy [15], and Santamaria et al. [16] which have also been considered in this paper for comparison. One of the best reaction mechanisms for OCM is given by Stansch et al. [8] who proposed a comprehensive ten-step ki- netic model of OCM on the basis of kinetic measurements in a catalytic fixed-bed micro-reactor covering a wide range of reaction conditions. The reaction scheme contains three pri- mary and seven consecutive steps. The conversion of hydro- carbons and of carbon monoxide with oxygen were described by applying Hougen-Watson type rate equations while for the other reactions power law rate equations were used. With this kinetic model, the experimentally determined conversions of methane and oxygen, as well as the yields of C 2+ hydrocar- bons and carbon oxides, could be predicted with an average accuracy of 20%. ∗ Corresponding author. Tel: +98-913-387-5507; E-mail: ali.farsi@gmail.com (A.Farsi) Copyright©2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved. doi:10.1016/S1003-9953(10)60179-X