Oxygen Permeation in Dense Ceramic Membranes

Figure 5.1 Oxygen permeation in dense ceramic membranes (a) electrochemical oxygen pump (b) oxygen permeation together with production of electricity ...

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Fermeation rate. From an economic point of view, the oxygen fluxes in the dense ceramic membranes are required to be higher than 5mL(STP) cm min" (or 1.9 x 10 molcm s ) so as to achieve commercial benefits [21]. However, most currently developed membranes exhibit much lower permeation rate than this. 

Dense ceramic membranes allow oxygen or hydrogen permeation in a dissociated or ionized form other than the conventional molecular diffusion, and thus exhibit extremely high selectivity (up to 100%). They can be incorporated into membrane reactors for a variety of oxidation and dehydrogenation reactions where the membrane functions as either a product extractor or a reactant distributor. Three configurations, that is, disc/flat-sheet, tubular and hollow fibre membranes have been applied in membrane reactors. They exhibit respective advantages/disadvantages in terms of the ease and cost of fabrication, the effective membrane area/volume ratio, and... 

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. 

Some materials, capable of being selectively permeated by only one gas, are present in nature. Generally speaking, almost all metals are permeable only to Hj, while other materials are capable of being selectively permeated only by oxygen. In particular, some dense materials (Pd and its alloys, Pt, V, Ta, Nb and SiOj ceramic membrane) exhibit signihcant H2 permeability... 

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