Boosting the gasoline production via a novel multifunctional Fischere Tropsch reactor: Simulation and optimization M. Bayat a , M.R. Rahimpour a, b, * a Department of Chemical Engineering, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 71345, Iran b Department of Chemical Engineering and Materials Science, University of California, Davis, One Shields Avenue, Davis, California 95616, United States article info Article history: Received 23 September 2012 Received in revised form 12 December 2012 Accepted 17 December 2012 Keywords: Gasoline production Multifunctional reactor FischereTropsch synthesis Differential evolution method abstract Energy and the environment are two of the most important issues this century. Multifunctional reactor has been recognized as one of the most promising configurations for simultaneous production of gasoline and hydrogen; as well stabilizing the atmospheric green house gases level. This paper focuses on mathematical modeling and optimization of a novel multifunctional reactor (MR) in order to enhance the production of gasoline and reduces CO 2 and CH 4 emission. FischereTropsch synthesis is carried out in exothermic side and supplies the necessary heat for the benzene synthesis reaction. The proposed reactor configuration consists of two catalytic fixed beds separated by the solid wall and also two Pd/Ag membranes, one is used for ultrapure hydrogen production from the endothermic side and the subse- quent is applied in order to selectively hydrogen addition to the exothermic side. A one-dimensional, steady-state heterogeneous model and the differential evolution (DE) method, as a strong and power- ful optimization method, are applied to simulate and optimize the proposed reactor configuration. The results of optimized multifunctional rector (OMR) represent 40.91% enhancement in the yield of gasoline in comparison with conventional FischereTropsch reactor (CR). Moreover, 75% and 34.46% decrease in the yield of methane and carbon dioxide as undesired products, respectively. On the other hand, a favorable temperature profile along the reactor length of OMR is achieved in comparison with CR. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Recently, the high oil price has created considerable interest in the development of alternative technology for the manufacture of transportation fuels. The gas-to-liquid (GTL) process can be a good candidate for alleviating the current oil crisis, in which synthetic liquid fuels (e.g., gasoline, diesel, and wax) are produced from stranded natural gas (Schulz, 1999; Hall, 2005). 1.1. FischereTropsch synthesis In the GTL process, FischereTropsch synthesis (FTS) is the key technology for converting synthesis gas (mixture of CO and H 2 ) to liquid fuels. The development of an effective catalyst and reactor system is the most competitive issue in FTS. FischereTropsch synthesis is classified into low temperature FischereTropsch (LTFT) process and high temperature FischereTropsch (HTFT) process depending on the type of the required products. Gasoline and linear olefins are produced mainly via high temperature process, but low temperature process is more often used to produce waxy materials (Akhtar et al., 2006). Marvast et al. (2005) simu- lated a 12 m long water-cooled fixed bed FeT reactor and investi- gated the effects of reactor temperature on gasoline production. In this study, the high temperature FischereTropsch carried out over Fe-based catalyst is considered. In conventional fixed bed Fischere Tropsch reactors, multitubular reactors cooled by saturated water are often used. A FT synthesis pilot plant was designed and con- structed by the Research Institute of Petroleum Industry (RIPI) and National Iranian Oil Company (NIOC) in 1999 (FischereTropsch pilot plant data). In FischereTropsch synthesis is very important to adjust a H 2 /CO ratio (Young et al., 2008). Feed H 2 /CO ratios of about 1 reduce the synthesis gas conversion and the CH 4 selectivity, while the C 5 þ selectivity and olefin/paraffin ratio for C 2 eC 4 is increased that is more suitable for high temperature FeT (HTFT) process. Moreover, it has been observed that the reacting gas is H 2 - poor in the second half of the reactor and hydrogen adding into the system is necessary. “H 2 -poor” means that the H 2 /CO ratio is lower than the optimum ratio what is required for C 5 þ production. Hence, * Corresponding author. Department of Chemical Engineering, School of Chem- ical and Petroleum Engineering, Shiraz University, Shiraz 71345, Iran. Tel.: þ98 711 2303071; fax: þ98 711 6287294. E-mail address: rahimpor@shirazu.ac.ir (M.R. Rahimpour). Contents lists available at SciVerse ScienceDirect Journal of Natural Gas Science and Engineering journal homepage: www.elsevier.com/locate/jngse 1875-5100/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jngse.2012.12.003 Journal of Natural Gas Science and Engineering 11 (2013) 52e64