Oxygen transport, dense ceramic

Dense ceramic ion-conducting membranes (CICMs) are emerging as an important class of inorganic membranes based on fluorite- or perovskite-derived crystalline structures [18]. Most of the ion-conducting ceramics discovered to date exhibit a selective ionic oxygen transport at high temperatures >700°C. Ionic transport in these membranes is based on the following successive mechanisms [25] ... 

FIGURE 6.32 Schematic diagram of an integrated distributor/extractor membrane reactor based on the combination of dense ceramic oxygen and hydrogen transport membrane for syngas production. 

The principles behind this membrane technology originate from solid-state electrochemistry. Conventional electrochemical halfceU reactions can be written for chemical processes occurring on each respective membrane surface. Since the general chemistry under discussion here is thermodynamically downhill, one might view these devices as short-circuited solid oxide fuel cells (SOFCs), although the ceramics used for oxygen transport are often quite different. SOFCs most frequently use fluorite-based solid electrolytes - often yttria stabUized zirco-nia (YSZ) and sometimes ceria. In comparison, dense ceramics for membrane applications most often possess a perovskite-related lattice. The key fundamental... 

Air separation membranes are typically dense ceramic (typically perovskite) membranes, which selectively permeate oxygen in ionic form. Over the past two decades. Air Products (ITMs) and Praxair (oxygen transport membranes [OTMs]) have worked towards the commercial scale-up of these membranes for applications in power generation, gasification, and gas to liquid conversion [94]. Air Products has focused on a planar configuration, whereas Praxair on tubular membranes. 

Maiya, P. S., Balachandran, U., Dusek, J. T., MieviUe, R. L., Kleelisch, M. S., Udovich, C. A. (1997). Oxygen transport by oxygen potential gradient in dense ceramic oxide membranes. 

Diethelm, S. and van Herle, J. (2004) Oxygen transport through dense Lao.6Sro.4Feo.8Coo.203 a perovskite-type permeation membranes. /. Eur. Ceram. Soc., 24, 1319-1323. 

Transport properties (separate determination of electronic and ionic conductivity, oxygen tracer diffusion and chemical diffusion) and surface stages (rate/constant of exchange) parameters of dense ceramics can be studied by several methods, such as electronic blocking polarization methods [32-34], O tracer profile analysis by SIMS [26, 27, 29, 35], study of the isotope exchange kinetics by gas-phase analysis of the isotope composition [27,... 

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