Membranes Methanol data

Methanol/toluene mixtures could be separated by pervaporation technique using PVA/PAcr.Ac. blend membranes. Reported data are presented in table 10. 

Struis and Stuck [6.12] have evaluated the application of membrane reactors for methanol synthesis using methanol permselective Nafion membranes. In their design calculations they utilize kinetic and membrane permeation data measured in their laboratory. They estimate that with 10 im thin membrane under methanol synthesis plant technically relevant conditions (T = 200 C, P = 40 bar, GHSV = 5000 h ), the single pass reactor yield improves by 40 %, and that the additional costs for the membrane materials correspond only to two production months. The ability of the Nafion membranes to withstand such conditions for prolonged periods still remains, however, questionable. 

The chapter also talked on various techniques developed for determining the membranes methanol permeability. Assessment of these techniques has shown that electrochemical techniques are more accurate. Among the elechochemical techniques, potentiometry has additional advantages of easier reproducibility of results, obtaining more data points, and convenience. 

Recent fuel cell membrane research and development (R D) efforts are summarized with a focus on (1) membranes for high-temperature, low-hmnidity PEMFC operation, (2) low-cost alternatives to PFSA membranes, and (3) direct methanol fuel cell membranes. A listing of fuel cell membrane performance data is given in Tables 29.4-29.6 for each membrane subcategory. The review material is by no means exhaustive, but it is representative of the kinds of fuel cell membranes previously/cmrently under investigation. For different viewpoints on the evolutionary development of various fuel cell membranes, the reader is directed to other review articles in the open hterature (Rikukawa and Sanui, 2000 Li et al., 2003 Haile, 2003 Jannasch, 2003 Savadogo, 2004 Hickner et al., 2004 Hogarth et al., 2005 Smitha et al., 2005). 

X-ray diffraction studies on gramicidin commenced as early as 1949 218-219> and this early work pointed to a helical structure 220). Recent work by Koeppe et al. 221) on gramicidin A crystallised from methanol (/%) and ethanol (.P212121) has shown that the helical channel has a diameter of about 5 A and a length of about 32 A in both cases. The inclusion complexes of gramicidin A with CsSCN and KSCN (P212121) have channels that are wider (6-8 A) and shorter (26 A) than the uncomplexed dimer 221 222). Furthermore there are two cation binding sites per channel situated either 2.5 A from either end of the channel or 2.5 A on each side of its centre 222) Unfortunately these data do not permit a choice to be made from the helical models (i)—(iv) and it is not certain if the helical canals studied are the same as those involved in membrane ion transport. 

Figure 20. Electro-osmotic drag coefficients of diverse membranes based on perfluorinated polymers (Dow - and Nafion/silica composites ) and polyarylenes (S—PEK/ PSU blends, ionically cross-linked S—PEK/PBP ), as a function of the solvent (water/methanol) volume fraction Xy (see text for references). Lines represent data for Nafion and S—PEK (given for comparison) for data points, see Figure 15. Dashed lines correspond to the maximum possible electro-osmotic drag coefficients for water and methanol, as indicated (see text).

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by ingestion, inhalation, and intravenous routes. Questionable carcinogen with experimental tumorigenic data. Experimental reproductive effects. A corrosive. A skin and severe eye irritant. An allergen. Has been reported as causing irritation of mucous membranes and heart rhythm disturbances in humans. Violent reaction with water -(above 30°C), acetone + water, methanol, methanol + sodium hydrogen carbonate, 2-ethoxyethanol, dimethyl formamide, 3-butanone + sodium hydroxide + water, allyl alcohol + sodium hydroxide + water (at 28°C). When heated to decomposition it emits toxic fumes of CL and NOx. See also CHLORIDES. 

In Fig. 11.7 the distribution of drugs belonging to several pharmacological clas.ses on the plane determined by the first two principal components account together for 81.5% of the variability in the retention data measured from 8 HPLC systems I50. The HPLC systems comprised stationary phases such as standard and specially deactivated hydrocarbonaceous silicas, polybutadiene-coated alumina, immobilized artificial membrane and immobilized Oi-acid glycoprotein. Methanol-buffer eluents of varying compositions and pH were used. The clustering of analytes is consistent with their estab-... 

Pinerii and coworkers, and a few other groups, have used ESR and Mossbauer spectroscopy as well as SANS, extended x-ray absorption fine structure (EX.AFS), and magnetization and susceptibility data to analyze local. struct.ure in perfluorinated ionomer membranes and the distribution of water within them isee, for inst,ance, (61-65) 1. The application of the KNDOR (electron nuclear double resonance) technique to deuteriated methanol-swollen Scunples of these membranes has been reportesd i-ecentiy (66). Photophysical methods have also tef n applied in hydration. si.udies of these membranes (67-69). Finally, some NMR results on the same hydrated perfluorinat,ed ionomer.s well as on hydrated... 

Experimental. The hollow fiber membranes used for this study were Naflon 811, which Is a copolymer of polysulfonyl fluoride vinyl ether and polytetrafiuoroethylene, and sulfonated and/or quaternated derivatives of polyethylene (kindly supplied by Dr. E. Korngold from Ben Gurlon University In Israel). The aqueous alcohol solutions studied thus far are those of methanol, ethanol and 2-propanol. The separations were accomplished via the pervaporatlon process as described In Reference 9. Counter Ions were replaced In the hollow fiber by soaking the permeator for twenty four hours In 1 molar solutions of the pertinent Ions. For example, experiments were conducted with Na as a counter Ion. When this set of experiments was finished, the sodium was exchanged by Ll etc. Each data point shown In Figure 14 consists of 6 to 10 measurements taken over a time period of 8 hours. Re-runs with the various counter Ions proved that the intrinsic properties of the membrane remain unchanged and the permeability measurements are reproducible. 

Kreuer et al. [25] investigated the membrane properties, including water sorption, transport (proton conductivity, electro-osmotic water drag and water diffusion), microstructure and viscoelasticity of the short-side-chain (SSC) perfluorosulfonic acid ionomers (PFSA, Dow 840 and Dow 1150) with different lEC-values. The data were compared to those for Nafion 117, and the implications for using such ionomers as separator materials in direct methanol and hydrogen fuel cells discussed. Tire major advantages of PFSA membranes were seen to be (i) a high proton conductivity. 

Previous work with aqueous solution systems has been successful In treating both completely Ionized salts as well as Incompletely Ionized salts (, 6). This work Incorporates both of these cases In methanol solutions and uses the Klmura-Sourlrajan analysis for the treatment of reverse osmosis data (.7). The surface excess free energy parameters (.-tAG/KT) for the Ions and Ion pairs Involved were determined by the methods established earlier (8). The predictability of membrane performance by the use of data on free energy parameters obtained In this work has been tested. 

The physicochemical criteria approach to reverse osmosis separations Involving the surface excess free energy of solvation for ionized and nonlonized solutes has been demonstrated by this work to include nonaqueous solutions. The parameters and correlations presented in this work permit the prediction of reverse osmosis separations and permeation rates for different alkali metal halides for cellulose acetate OEastman E-398) membranes of different surface porosities from only a single set of experimental data for a sodium chloride-methanol reference feed solution system. 

Reverse osmosis separations of 12 alkali meteil halides in methanol solutions have been studied using cellulose acetate membranes of different surface porosities. Data for surface excess free energy parameters for the ions and ion pairs Involved have been generated for the above mend>rane material-solution systems. These data offer a means of predicting the performance of cellulose acetate membranes in the reverse osmosis treatment of methanol solutions involving the above ions from only a single set of experimental data. 

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