Membrane ketone

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

Health and Safety Factors. Like other low molecular weight ketones, MIBK is an anesthetic chemical with no highly cumulative toxicological effects. Inhalation of vapors can irritate mucous membranes. 

Asphalt Asphalt is used as a flexible protective coating, as a bricklining membrane, and as a chemical-resisting floor covering and road surface. Resistant to acids and bases, alphalt is soluble in organic solvents such as ketones, most chlorinated hydrocarbons, and aromatic hydrocarbons. 

Diethyl pyrocarbonate (DEP) [1609-47-8] M 162.1, b 38-40°/12mm, 160-163 /atm, d 1.119, Op 1.398. Dissolve in Et20, wash with dilute HCl, H2O, dry over Na2S04. filter, evaporate and distil the residue first in vacuo then at atmospheric pressure. It is soluble in alcohols, esters, ketones and hydrocarbon solvents. A 50% w/w soln is usually prepared for general use. Treat with great CAUTION as DEP irritates the eyes, mucous membranes and skin. [Boehm and Mehta Chem Ber 71 1797 1938 Thoma and Rinke Justus Liebigs Ann Chem 624 30 1959.]... 

An HFRO module with a membrane area of 300 m is used to teraove methyl ethyl ketone (MEK) from wastewater. The feed to the module has a flowrate of 9 x 10 m /s, an MEK composition of 9500 ppm, and an osmotic pressure of 5.2 atm. The average pressure difference across the membrane is 50 atm. The permeate is collected at atmos eric pressure. The water recovery for the module is 86%, and the solute rejection is 98%. Evaluate the transport parameters Ay and (p ujKS). 

Ketone body synthesis occurs only in the mitochondrial matrix. The reactions responsible for the formation of ketone bodies are shown in Figure 24.28. The first reaction—the condensation of two molecules of acetyl-CoA to form acetoacetyl-CoA—is catalyzed by thiolase, which is also known as acetoacetyl-CoA thiolase or acetyl-CoA acetyltransferase. This is the same enzyme that carries out the thiolase reaction in /3-oxidation, but here it runs in reverse. The second reaction adds another molecule of acetyl-CoA to give (i-hydroxy-(i-methyl-glutaryl-CoA, commonly abbreviated HMG-CoA. These two mitochondrial matrix reactions are analogous to the first two steps in cholesterol biosynthesis, a cytosolic process, as we shall see in Chapter 25. HMG-CoA is converted to acetoacetate and acetyl-CoA by the action of HMG-CoA lyase in a mixed aldol-Claisen ester cleavage reaction. This reaction is mechanistically similar to the reverse of the citrate synthase reaction in the TCA cycle. A membrane-bound enzyme, /3-hydroxybutyrate dehydrogenase, then can reduce acetoacetate to /3-hydroxybutyrate. 

Organic solutions can be obtained in high yield by extracting HOCl from Cl -containing aqueous solutions into polar solvents such as ketones, nitriles or esters. Electrodialysis using semiper-meable membranes affords an alternative route. 

Sulfonated hydroquinone was used to prepare functional poly(arylene ether ketone)s, which may be used a gas separation membranes.202... 

The use of such an oxazaborolidine system in a continuously operated membrane reactor was demonstrated by Kragl et /. 58] Various oxazaborolidine catalysts were prepared with polystyrene-based soluble supports. The catalysts were tested in a deadend setup (paragraph 4.2.1) for the reduction of ketones. These experiments showed higher ee s than batch experiments in which the ketone was added in one portion. The ee s vary from 84% for the reduction of propiophenone to up to >99% for the reduction of L-tetralone. The catalyst showed only a slight deactivation under the reaction conditions. The TTON could be increased from 10 for the monomeric system to 560 for the polymer-bound catalyst. 

Acid and base extractions from this material have been shown to form spontaneous structures in solution termed coercevates that could easily form the basis for protypical membranes (more of this in Chapter 9). Hydrocarbons with chain lengths C15-C30 (both straight and branched chains) and of course PAHs, predominantly pyrene and fluoranthrene, polar hydrocarbons such as aromatic ketones, alkyl and aryl ketones, nitrogen and sulphur heterocycles and most intriguingly purine and pyrimidine analogues have all been observed from this rich carbonaceous cocktail of compounds. Why ... 

Oxidative damage to membrane polyunsaturated fatty acids leads to the formation of numerous lipid peroxidation products, some of which can be measured as index of oxidative stress, including hydrocarbons, aldehydes, alcohols, ketones, and short carboxylic acids. 

Ramani, V., Swier, S., Shaw, M. T, Weiss, R. A., Kunz, H. R., and Fenton, J. M. Membranes and MEAs based on sulfonated poly(ether ketone ketone) and heteropolyacids for polymer electrolyte fuel cells. Journal of the Electrochemical Society 2008 155 B532-B537. 

Proton conductivity as a function of lEC for ETFE-g-PSSA = polyethylenetetrafluoroethylene-gra/t-polystyrene sulfonic acid, BAM membrane = substituted poly(trifluorostyrene) sulfonic acid, SPEEK = sulfonated poly(ether ether ketone) and Nafion. (From Peckham, T. J. et al. 2007. Journal of Materials Chemistry 17 3255-3268, and Dolye, M. et al. 2001. Journal of Physical Chemistry B 105 9387-9394.)... 

Another concern for polystyrene- and some aromatic-based PEMs is hydrolysis of fhe sulfonic acid group from aromatic rings as well as hydrolytic cleavage of polymer backbone under fuel cell conditions for aromafic polymers including polyimides, poly(arylene ethers), poly(ether ketones), and poly(ether sulfones). It is well known that the sulfonation of aromafic rings is a reversible process especially at low pH and at elevated temperature (Scheme 3.3). The reversibility of sulfonation, for example, is used in fhe preparafion of trinitrotoluene or picric acid. Por the simplest membrane of the class of arylsulfonic acids (i.e., benzenesulfonic acid), fhe reacfion occurs upon freatment with a stream of superheated steam at 180°C.i ... 

Xing, P., Robertson, G. R, Guiver, M. D., Mikhailenko, S. D. and Kaliaguine, S. 2004. Sulfonated poly(aryl ether ketone)s containing the hexafluoroisopro-pylidene diphenyl moiety prepared by direct copolymerization, as proton exchange membranes for fuel cell application. Macromolecules 37 7960-7967. 

Wang, E, Li, J., Chen, T. and Xu, J. 1999. Synthesis of poly(ether ether ketone) with high content of sodium sulfonate groups and its membrane characteristics. Polymer 40 795-799. 

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