Asymmetric oxygen-permeable membrane synthesis and its utilization for methane oxidation

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A disk-type Sm_<0.4>Ba_<0.6>Co_<0.2>Fe_<0.8>O_<3-δ> 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_2O react with CH_4 by reforming reactions to form syngas.