Membrane separation devices

Kusakabe et al. prepared yttria-stabilised zirconia membranes on a-alumina tubes and impregnated them with platinum and rhodium for the preferential oxidation of carbon monoxide [530]. The carbon monoxide concentration could be decreased from 10 000 ppm in the feed to 30 ppm in the permeate, at 150 °C reaction temperature by the platinum containing membrane. However, the ceramic membrane also showed permeance for carbon dioxide and methane. The latter was oxidised to a certain extent over the platinum catalyst of the membrane. The rhodium catalyst showed inferior performance and even some activity towards methanation at a 250 °C reaction temperature in the absence of oxygen in the feed. 

Membrane separation (see also Section 5.2.4) as a unit operation is available for many applications on an industrial scale. However, for smaller scale mobile applications the separation unit is, in most instances, integrated into the reformer or water-gas shift reactor forming so-called membrane reactors, which were presented in Sections 7.1.4, 7.2.3 and 7.3.4. Some examples of fabrication technologies for membranes will be discussed in Section 10.2.5, and examples of membrane separation devices without the presence of chemical reactions will be presented below. 

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Wimer, J.G. Williams, M.C. Archer, D.H. Osterle, J.F. Networking Electrochemical Membrane Separation Devices ... 

FIGURE 49 (a) Plasmapheresis system and (b) rotating membrane separation device. (Source Baxter Healthcare Corporation.)... 

Membrane separation devices are assembled in a number of forms. In a flat sheet form the membrane is laid over a flat porous support. A unit would include a large number of the flat sheets separated by spacers and stacked together. In another configuration the fiat sheet may be spiral-wound with spacers around a perforated tube. Other arrangements involve tubular membranes or hollow fiber membranes assembled in bundles. In the tubular module the membrane is wrapped around a tubular... 

Figure P13.15 Continuous culture of yeast in a CSTBR with recycle of cells using a membrane separation device from which the retentate is returned to the CSTBR.

D.R Reddy, Spiral-wound membrane separation device with feed and permeate/sweep fluid flow control, US Patent 5,096,584. 

The selectivity to vards carbon monoxide is of course no longer an issue when methanation is applied for the removal of traces of carbon monoxide from purified hydrogen permeate dovmstream of a membrane separation device. The carbon dioxide concentration is then as low as the carbon monoxide concentration and the parallel conversion of both carbon oxides becomes viable (see Section 5.2.4). 

A membrane separation device was prepared by Wilhite et al. by micro-electromechanical techniques [526]. The palladium/silver membrane deposited onto a silicon oxide support was only 20-nm thick, which was possibly the lowest membrane thickness ever reported for hydrogen separative purposes. A lanfhanum/nickel/cobalt oxide catalyst (LaNi0.95Co0.05O3) catalyst for partial oxidation of methanol was deposited onto the membrane. At a O/C ratio of 0.86 and 475 °C reaction temperature, up to 64% methanol conversion and more than 90% hydrogen selectivity could be achieved. These workers claimed a deviation from Sievert s law (see Section 5.2.4) for their membrane. N amely, the hydrogen flux did not depend by a power of 0.5 of the retenate and permeate pressure but rather by a power of 0.97, which they attributed to the absence of internal solid-state diffusion limitations in their ultra-thin membrane. 

OLMES is a project that looks at the application of CFD to the design of membrane separation devices used in the production of reformulated gasoline. To date, the primary method available for olefin reduction in FCC-derived gasoline is... 

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