The role of interfaces in ceria-based multi-phase membranes for membrane reactors

催化剂涂覆的O2渗透膜反应器的应用是多相催化领域中商业应用的合成方法的节能替代方案。在这样的处理过程中，转化所需的氧气取自空气。O2-离子通过气密的薄陶瓷层直接传输到催化剂。由于大多数转化发生在200 - 500 °C的温度范围内，因此在此温度范围内，特定渗透速率约为1 mlN cm-2 min-1的膜对于确保显著的转化率是必要的。通过陶瓷氧渗透膜的渗透通过固态扩散发生并且主要取决于双极电导率，具有一种主要的氧化物离子传导组分和一种电子传导组分的陶瓷复合材料是这种应用的有希望的候选者，因为这些材料联合收割机结合了高氧通量和高机械和化学性能。反应条件下的稳定性。然而，迄今为止的研究工作一直集中在700 °C以上的温度状况。为了在较低的温度范围内也达到良好的渗透速率，除了组合物的基本调整之外，主要的努力将是优化单一组分之间的界面。原因是在界面处发生各种反应，在本项目的过程中，该联盟计划系统地研究不同界面的化学和物理特性，或者更确切地说，研究在受体掺杂的CeO 2-SiO2界面处发生的传输过程。以尖晶石相作为电子传导组分的基于复合材料，其中FeCo 2 O 4将是初始材料。 更精确地理解晶界和三相边界的过程是有计划有目的地优化催化应用复合材料的关键，例如通过微结构化或调整不同相的化学组成。所选择的复合材料计划作为一系列CeO 2基多相复合材料的例子。从这些调查的基本见解将被用来达到在中间温度下的技术相关的渗透率，从而打开一个更广泛的应用领域的膜反应器的工作概念。

The application of catalyst-coated O2-permeable membrane reactors is an energy efficient alternative to the commercially applied methods of synthesis in the area of heterogeneous catalysis. During such treatments, the oxygen which is necessary for conversion is taken from air. O2- ions are transported straight to the catalyst through a gastight thin ceramic layer. This combines the two steps of air separation and chemical conversion in one process.As most of these conversions take place at temperatures between 200 and 500 °C, membranes with a specific permeation rate of roughly 1 mlN cm-2 min-1 in this temperature range are necessary to ensure a significant conversion rate. The permeation through a ceramic oxygen permeation membrane takes place by solid state diffusion and mainly depends on the ambipolar conductivity, the thickness of the membrane and the oxygen partial pressure gradient across the membrane.Ceramic composites with one mainly oxide ion conductive and one electron conductive constituent are promising candidates for this kind of application as these materials combine a high oxygen flux with high mechanical and chemical stability under reaction conditions. However, research efforts so far have been focused on the temperature regime above 700 °C. To reach a good permeation rate also in the lower temperature range, the main effort, apart from basic adaption of the composition, will be the optimization of the interfaces between the single constituents. The reason is that a variety of reactions occur at the interfaces, which have a fundamental impact on the oxygen transport through the membrane.In course of the present project the consortium plans to systematically investigate the chemical and physical characteristics of the different interfaces or rather of transport processes taking place at the interfaces of an acceptor doped CeO2-based composite material with a spinel phase as electron conductive constituent, where FeCo2O4 will be the initial material. A more precise comprehension of the processes at grain boundaries and triple phase boundaries is the key for the planned purposeful optimization of the composite material for catalytic applications, e.g. by micro structuration or adaption of the chemical composition of the different phases. The chosen composites are planned to serve as examples for a series of CeO2-based multiphase composites. The fundamental insights from these investigations will be used to reach technologically relevant permeation rates at intermediate temperatures and thus to open a broader field of application to the working concept of a membrane reactor.