By-products water

Polymer Electrolyte Fuel Cell. The electrolyte in a PEFC is an ion-exchange (qv) membrane, a fluorinated sulfonic acid polymer, which is a proton conductor (see Membrane technology). The only Hquid present in this fuel cell is the product water thus corrosion problems are minimal. Water management in the membrane is critical for efficient performance. The fuel cell must operate under conditions where the by-product water does not evaporate faster than it is produced because the membrane must be hydrated to maintain acceptable proton conductivity. Because of the limitation on the operating temperature, usually less than 120°C, H2-rich gas having Htde or no (

By-product water formed in the methanation reactions is condensed by either refrigeration or compression and cooling. The remaining product gas, principally methane, is compressed to desired pipeline pressures of 3.4—6.9 MPa (500—1000 psi). Einal traces of water are absorbed on siHca gel or molecular sieves, or removed by a drying agent such as sulfuric acid, H2SO4. Other desiccants maybe used, such as activated alumina, diethylene glycol, or concentrated solutions of calcium chloride (see Desiccants). 

Depending on the requirements of the chemical procedure, the processing method may be varied with different mechanical arrangements to remove the by-product, water, in order to drive the esterification reaction toward completion. 

Reaction of 1-pentanol with propionic acid provides 1-pentyl propionate [624-54-4] a new coatings solvent for automotive refinish and OEM paints, apphances, and for higher-solids systems (37). The esterification of 1-pentanol with formic acid to 1-pentyl formate [638-49-3] is conducted by concomitant removal of by-product water by a2eotropic distillation with diethyl ether (38). 

The conversion of the intermediate bromo aldehyde to the dioxane proceeds readily owing to a favorable equilibrium position. However, the equilibrium for the reaction of the bromo ketone with the diol is unfavorable and requires removal of the by-product, water. This is done under mild conditions using... 

RCO2H, R OH, DCC/DMAP, Et20, 25°, 1-24 h, 70-95% yield. This method is suitable for a large variety of hindered and unhindered acids and alcohols." Carbodiimide i was developed to make the urea by-product water soluble and thus easily washed out. ... 

From the preceding discussion, it is easily understood that direct polyesterifications between dicarboxylic acids and aliphatic diols (Scheme 2.8, R3 = H) and polymerizations involving aliphatic or aromatic esters, acids, and alcohols (Scheme 2.8, R3 = alkyl group, and Scheme 2.9, R3 = H) are rather slow at room temperature. These reactions must be carried out in the melt at high temperature in the presence of catalysts, usually metal salts, metal oxides, or metal alkoxides. Vacuum is generally applied during the last steps of the reaction in order to eliminate the last traces of reaction by-product (water or low-molar-mass alcohol, diol, or carboxylic acid such as acetic acid) and to shift the reaction toward the... 

The interfacial area AtV usually excludes the contact area between the vapor space and the liquid at the top of the reactor. The justification for this is that most gas-liquid reactors have gas bubbles as a dispersed phase. This gives a much larger interfacial area than the nominal contact area at the top of the reactor. There are exceptions—e.g., polyester reactors where by-product water is removed only through the nominal interface at the top of the reactor— but these are old and inefficient designs. This nominal area scales as while the contact area with a dispersed phase can scale as S. 

Semibatch or fully continuous operation with continuous removal of a by-product gas is also common. It is an important technique for relieving an equilibrium limitation, e.g., by-product water in an esterification. The pressure in the vapor space can be reduced or a dry, inert gas can be sparged to increase Ai and lower a, thereby increasing mass transfer and lowering u/ so that the forward reaction can proceed. 

Chimenos, J.M. et al.. Removal of ammonium and phosphates from wastewater resulting from process of cochineal extraction using MgO-containing by-product. Water Res., 37, 1601, 2003. 

The oxidation of cobalt metal to inactive cobalt oxide by product water has long been postulated to be a major cause of deactivation of supported cobalt FTS catalysts.6 10 Recent work has shown that the oxidation of cobalt metal to the inactive cobalt oxide phase can be prevented by the correct tailoring of the ratio Ph2cJPh2 and the cobalt crystallite size.11 Using a combination of model systems, industrial catalyst, and thermodynamic calculations, it was concluded that Co crystallites > 6 nm will not undergo any oxidation during realistic FTS, i.e., Pi[,()/I)i,2 = 1-1.5.11-14 Deactivation may also result from the formation of inactive cobalt support compounds (e.g., aluminate). Cobalt aluminate formation, which likely proceeds via the reaction of CoO with the support, is thermodynamically favorable but kinetically restricted under typical FTS conditions.6... 

The esterification by-product, water, is removed via a process column in a continuous steady-state mode of operation. The bottom product of the column, being mainly EG, flows back into the esterification reactor. The condensed top product consists mainly of water with small traces of EG. In cases where a reverse-osmosis unit is connected to the distillate flow line, the residual EG can be separated very efficiently from the water [124], The combination of a process column with reverse osmosis saves energy cost and capital investment. The total organic carbon (TOC) value of the permeate is sufficiently low to allow its discharge into a river or the sea without any environmental impact. 

The bulk of the effluent is run through a cooler (heat exchanger) and a condenser to remove the light ends that include traces of carbon monoxide and carbon dioxide and by-product water. The bottom stream is maleic acid, which is easily dehydrated, as in Figure 20—4, by vacuum distillation or azeotropic distillation with ortho-xylene. See Chapter 3 if youVe forgotten totally everything about azeotropic distillation.) The dehydrated maleic acid is maleic anhydride. Further purification is done by distillation.,... 

This is to assume that a dry membrane is hydrated by production water generated at the current density, I. For Nafion 112 and a reference current density of 1 A/cm, this is about 25 s Therefore, for low humidity cells where the membrane undergoes water content changes, the water accumulation term is essential for transient analyses. 

Choi J, Valentine RE (2002) Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine a new disinfection by-product. Water Res 36(4) 817-824... 

The polymerization between equimolar amounts of a diol and diacid proceeds with an equilibrium constant of 200. What will be the expected degree of polymerization and extent of reaction if the reaction is carried out in a closed system without removal of the by-product water To what level must [H20] be lowered in order to obtain a degree of polymerization of 200 if the initial concentration of carboyxl groups is 2 Ml... 

Oxygen, a highly useful gas, is the only by-product. Water electrolyzers today satisfy approximately 3.9% of the world s... 

Carlton BD, Smith MK. 1985. Reproductive effects of alternate disinfectants and their by-products. Water chlorination chemistry, environmental impact and health effects. In Proceedings of the fifth conference on water chlorination- environmental impact and health effeets, Williamsburg, Virginia, June 3-8, 1984. Chelsea, MI Lewis Publishers, Inc., 295-305. 

For the synthesis of chemicals from CO/H2 three considerations will influence the economics and process feasibility, namely the ratio of C0 H2, the loss of oxygen as by-product water or CO2, and the interrelation of chemicals/fuels. The two first points are exemplified in Table I. 

In light of the importance of water storage in partially dry membranes, it is instructive to correlate the cold-start performance quantified by product water (mElo, mg/cm2) with the membrane water uptake potential (Ak) defined as ... 

Kitis, M., Kilduff, J. E., and Karanfil,T. (2001). Isolation of dissolved organic matter (DOM) from surface waters using reverse osmosis and its impact on the reactivity of DOM to formation and speciation of disinfection by-products. Water Res. 35, 2225-2234. 

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