Reaction and oxygen permeation studies in Sm 0.4 Ba 0.6 Fe 0.8 Co 0.2 O 3  d membrane reactor for partial oxidation of methane to syngas Masayuki Ikeguchi a , Tomohiro Mimura a , Yasushi Sekine b , Eiichi Kikuchi a,b , Masahiko Matsukata a,b, * a Department of Applied Chemistry, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan b Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan Received 13 January 2005; received in revised form 18 May 2005; accepted 27 May 2005 Available online 11 July 2005 Abstract A disk-type Sm 0.4 Ba 0.6 Co 0.2 Fe 0.8 O 3  d perovskite-type mixed-conducting membrane was applied to a membrane reactor for the partial oxidation of methane to syngas (CO + H 2 ). The reaction was carried out using Rh (1 wt%)/MgO catalyst by feeding CH 4 diluted with Ar. While CH 4 conversion increased and CO selectivity slightly decreased with increasing temperature, a high level of CH 4 conversion (90%) and a high selectivity to CO (98%) were observed at 1173 K. The oxygen flux was increased under the conditions for the catalytic partial oxidation of CH 4 compared with that measured when Ar was fed to the permeation side. We investigated the reaction pathways in the membrane reactor using different membrane reactor configurations and different kinds of gas. In the membrane reactor without the catalyst, the oxygen flux was not improved even when CH 4 was fed to the permeation side, whereas the oxygen flux was enhanced when CO or H 2 was fed. It is implied that the oxidation of CO and H 2 with the surface oxygen on the permeation side improves the oxygen flux through the membrane, and that CO 2 and H 2 O react with CH 4 by reforming reactions to form syngas. # 2005 Elsevier B.V. All rights reserved. 1. Introduction Researchers are seeking methods to convert methane to syngas, which is a mixture of carbon monoxide and hydrogen, as a way to utilize natural gas. Syngas can be further converted into liquid fuels such as gasoline and methanol, which are more convenient for transportation and storage than natural gas. Syngas can be produced from methane using an oxygen permeable membrane reactor for the partial oxidation of methane [1–10]. Dense oxygen ionic-electronic mixed- conducting ceramic membranes are applied to the membrane reactor to separate pure oxygen from air at high temperatures by dissociating and reducing the oxygen molecules on the surface of the mixed-conducting oxide and transporting the oxygen as lattice oxygen ions. In the membrane reactor, methane is converted by oxygen permeated through the membrane from air; the process therefore does not require expensive cryogenic oxygen production apparatus. The reaction heat of the exothermic partial oxidation of methane is sufficient for the membrane reactor process to be self-standing. The H 2 /CO ratio of the product obtained by the partial oxidation process can be 2, which is a suitable ratio for methanol synthesis and for the Fisher-Tropsch reaction to produce linear hydro- carbons. Since Teraoka et al. reported a mixed-conducting membrane: La x Sr 1x Co y Fe 1y O 3d [11] with high oxygen permeabilities, various types of mixed-conducting mem- branes with perovskite (ABO 3 ) or related structures such as SrFeCo 0.5 O x [1], Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3  d [5,6,12] and La x A 1  x Co y Fe 1  y O 3  d (A = Sr, Ba) [2–4,13–15] have been reported. Disk and tube-type membrane reactors have been reported for syngas production [1–10]. In some of these reports, both the high CH 4 conversion (>90%) and the high CO selectivity (>90%) are achieved by optimizing reaction conditions, while a wide variety of membrane www.elsevier.com/locate/apcata Applied Catalysis A: General 290 (2005) 212–220 * Corresponding author. Tel.: +81 3 5286 3850; fax: +81 3 5286 3850. E-mail address: mmatsu@waseda.jp (M. Matsukata). 0926-860X/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2005.05.033