Membranes, hydrocarbon

The hydrocarbon membrane can also operate at higher temperatures, of up to 95°C, which allows the use of smaller radiators to dissipate heat. It also lasts 50% longer, while generating up to 15% more power and operating at lower humidity levels. Fluorocarbon membranes can cost about 300 per square meter, the PolyFuel materials cost about half of this. While hydrocarbon membranes may have to prove themselves to many, Honda s FCX fuel cell cars use them. 

S. Tsushima, S. Hirai, K. Kitamura, M. Yamashita, S. Takasel, MRI application for clarifying fuel cell performance with variation of polymer electrolyte membranes Comparison of water content of a hydrocarbon membrane and a perfluorinated membrane. Appl. Magn. Reson. 32, 233-241 (2007)... 

PBI (see chemical structure above) is a hydrocarbon membrane that has been commercially available for decades. Free PBI has a very low proton conductivity ( 10 S/cm) and is not suitable for PEM fuel cell applications. However, the proton conductivity can be greatly improved by doping PBI with acids such as phosphoric, sulfuric, nitric, hydrochloric, and perchloric acids. The PA-doped PBI membrane is the most popular one in PEM fuel cell applications because H3PO4 is a nonoxidative acid with very low vapor pressure at elevated temperature. Savinell et al. and Wainright et al. first demonstrated the use of PBI-PA for HT fuel cells in 1994.270 272 since then, there has been a significant amount of research on the PBI-based membrane because of its low cost and good thermal and chemical stabil-... 

In addition to PBI, there are many other hydrocarbon membranes that can also serve as proton-conducting membranes. Most of them have been developed for automotive and DMFC applications. The driving forces for hydrocarbon membranes are the need for a low-cost membrane electrolyte with a wide operating temperature... 

Polyarylenes, in particular different types of poly(arylene ether ketone)s, have been the focus of much hydrocarbon membrane research in recent years. - - With good chemical and mechanical stability under PEM fuel cell operating conditions, the wholly aromatic polymers are considered to be the most promising candidates for high-performance PEM fuel cell applications. Many different types of these polymers are readily available and with good process capability. Some of these membranes are commercially available, such as poly(arylene sulfone)s and poly(arylene... 

No structural information is available from the manufacturer, but these hydrocarbon membranes are believed to be a part of the poly(arylene ether) family. Hoku Scientific, Inc., reported 2,000-h test data operating with H2-air. ... 

Kreuer, K.D., Hydrocarbon membranes, in Handbook of Fuel Cells Fundamentals, Technology, and Applications, 1st ed., Vielstich, W., Lamm, A., and Gasteiger, H.A., Eds., John Wiley Sons, West Sussex, England, 2003, p. 420. 

Shindo, D., HOKU hydrocarbon membrane, in 2006 Fuel Cell Seminar, Honolulu, HI, November 13-18, 2006, p. PT4. 

DMFC hydrocarbon membrane made by Polyfuel, Mountain View. 

Liquid membranes are double emulsions formed when a water-in-oil emulsion (w/o) is gently dispersed in a second aqueous phase, the external aqueous phase. The internal (emulsified) and external aqueous phases are kept separate by a layer of hydrocarbon, forming the liquid membrane. Since the two aqueous phases are not in contact, LM systems can be useful for separation processes as well as for enzyme immobilization separation is accomplished by selective transport of solutes across the hydrocarbon "membrane," and enzyme immobilization is accomplished by encapsulating enzyme(s) via emulsification of an aqueous enzyme solution. It is in fact possible to combine enzymatic reaction(s) with separations in a single LM system. Figure 1 depicts an LM-enzyme system. 

Fluorocarbon membranes can cost about 300 per square meter, the PolyFuel materials should cost about half of this. While hydrocarbon membranes have yet to prove themselves to many, Honda s latest FCX fuel cell cars use them. 

These compounds are synthesized by the copolymerization of tetrafluoroethylene and alkyl vinyl ether with sulfonyl acid fluoride. Preparation of sulfonyl acid fluoride takes place by pyrolysis of the respective oxide to give the olenfinated structure [7], The thermoplastic produced is extruded into a film. The sulfonyl fluoride (-S02F) group present in the thermoplastic is converted to sulfonate (-S()3 Na+) with NaOH. This is called the neutral form of Nafion, and it is converted to the acid for and cast into a thin film by heating in alcohol at 250°C. At around 650/m2, the Nafion membranes are rather expensive when compared to hydrocarbon membranes, which are also used. 

CO2 hydrogenation to produce methanol in a membrane reactor at low temperatures (<200 C) has been studied by Struis et al. [2.424]. Their study utilized Li-exchanged per-fluorinated hydrocarbon membranes, which selectively permeated both products of the reaction (H2O and CH3OH). Polymeric membranes (PDMS, polyamide) impregnated with... 

C.H. Park, C.H. Lee, M.D. Guiver, Y.M. Lee, Sulfonated hydrocarbon membranes for medium-temperature and low-humidity proton exchange membrane fuel cells (PEMFCs). Progress in Polymer Science 2011, 36(11), 1443-1498. 

Decrease in swelling and methanol cross leak of membranes in DMFC applications is one of the most important development items, and various efforts and trials have been performed to improve these characteristics for both perfluorinated and hydrocarbon membranes. 

Halwachs et al. studied the peimeation of hydrocaibons through oil-water-oil systems. They found that the most important variables governing the peimeation rates were membrane viscosity, type and concentration of surfactant, and ionic strength of the medium. However, the permeation rates of hydrocarbons through aqueous membranes were several orders of magnitude slower than the permeation rates of phenol through hydrocarbon membranes. ... 

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