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

将Sm_<0.4>Ba_<0.6>Co_<0.2>Fe_<0.8>O_<3-δ>钙钛矿型混合导电膜应用于膜反应器，用于甲烷部分氧化制合成气（CO + H_2）。以Rh (1wt %)/MgO为催化剂，用ar稀释CH_4进行反应。随着温度的升高，CH_4转化率提高，CO选择性略有降低，但在1173 K时CH_4转化率高（90%），CO选择性高（98%）。在CH_4部分氧化条件下，氧通量比在渗透侧添加Ar时有所增加。采用不同的膜反应器结构和不同种类的气体，研究了膜反应器内的反应途径。在无催化剂的膜反应器中，即使向渗透侧注入CH_4，氧通量也没有提高，而向渗透侧注入CO或H_2时，氧通量提高。这说明CO和H_2与渗透侧表面氧的氧化作用提高了膜上的氧通量，CO_2和h2o与CH_4发生重整反应生成合成气。

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.