Mixed-conducting oxygen permeable ceramic membrane and its application in the production of synthesis gas

Mixed conducting oxygen permeable ceramic membranes (O-MIEC) can simultaneously transport both oxygen ions and electrons without the requirement of an external circuit. One valuable application is to be used as the membrane reactor in the production of synthesis gas (mixture gas of CO and H2). The O-MIEC membrane reactors have unique advantages, such as avoiding conventional cryogenic separation and providing staged oxygen to the reactions. However, low oxygen permeability still hinders the industrial application of O-MIEC ceramic membranes.;Compared to other O-MIEC materials, Ba0.5Sr0.5Co 0.8Fe0.2Ox (BSCF) has relatively high oxygen permeability. This study detailedly investigated the effects of the preparation parameters (including pH, pressing pressure, preparation of green powders, and sintering profile of the membrane) on the performance of BSCF membranes. In addition, the dominant step of the oxygen permeation through the BSCF membrane was determined. The results show that bulk diffusion dominates the oxygen permeation. According to the analysis of the dominant step, a BSCF membrane with asymmetric geometry was fabricated using the dry-pressing method. The BSCF asymmetric membrane exhibits higher oxygen flux than the dense membrane.;The reaction performance of BSCF asymmetric membranes in the production of synthesis gas (the partial oxidation and CO2 reforming of CH 4) was studied, in which the role of the membranes in the reactions was investigated. The results show that BSCF asymmetric membranes maintained good integrity and stability in the reactions. The oxygen flux of BSCF asymmetric membrane was further increased when the membrane was exposed to the reaction. For the CO2 reforming reaction, high oxygen flux of BSCF asymmetric membrane enhanced the conversion of CH4 dramatically. Meanwhile, the reaction mechanism involved the oxidation of hydrogen and steam reforming due to the presence of a large amount of oxygen. For the partial oxidation of CH4, the high oxygen flux of BSCF asymmetric led to a high conversion of CH4 and H2 selectivity. Further analysis showed that the BSCF membranes actively participate in both the CO2 reforming and partial oxidation of CH4 reaction instead of being only an oxygen provider.