Ethylene glycol vapour pressure

We pass ethene and water (as a vapour) at high pressure over a suitable catalyst, causing water to add across the double bond of the ethene molecule. The industrial alcohol is somewhat impure because it contains trace quantities of ethylene glycol (1,2-dihydroxyethane, III), which is toxic to humans. It also contains unreacted water, and some dissolved ethene. 

Figure 2.25 Vapour pressures of acetaldehyde, water, dioxane, ethylene glycol and diethylene glycol, where the data have been calculated from the database of the commercial process simulator Chemcad (Chemstations)...

Other methods of surface area determination depend, in general, on adsorption under well defined conditions of various solute molecules of known dimensions (Sposito, 1984 Davis and Kent, 1990). Some of these are dipole molecules so that dipole interactions with the surface or H-bonding are involved. Water adsorbed at a fixed relative water vapour pressure (e. g. 0.2) to provide a monolayer is one example (Torrent et ah, 1990). An organic dipole frequently used for soils is ethylene glycol monoethylether (EGME) (Carter et al., 1965). The main problem with these dipole molecules lies in their mutual association which may lead to localized adsorption beyond a monolayer (capillary condensation), particularly on porous material. 

Ethylene glycol has a vapour pressure of 20mbar at 100 °C. Butanol has a vapour pressure of 500 mbar at approximately the same temperature. The boiling temperatures for butanol and ethylene glycol at normal atmospheric pressure are 117.9 °C and 198 °C, respectively. 

Ambrose, D., Hall, D.J. (1981) Thermodynamic properties of organic oxygen compounds. L. The vapour pressures of 1,2-ethanediol (ethylene glycol) and bis(2-hydroxyethyl) ether (diethylene glycol). J. Chem. Thermodyn. 13, 61-66. 

Ethylene glycol or 1,2-ethanediol is a colourless hygroscopic liquid with low vapour pressure. Neither it nor propylene glycol (1,2-propanediol) is toxic. 

The temperature of the available cooling water and the possible condensation pressure can preclude the use of a special motive medium. Also, the variation of the vapour pressure diagram by the addition of other components must be regarded. The example of the twin component system, ethylene glycol/water, makes this point more clearly. Even small parts of water lead to a distinct decrease of the necessary cooling liquid temperature. For example, at 2 mbar and a water content of 1% condensation is possible at 35 °C, but even at 3% water content the condensation temperature has decreased to about 15 C. 

Vapour pressure determinations in ternary systems with poly (vinylpyrrolidine) [157], 1-al l (butyl-, heptyl- and octyl-)-3-3methylidazolium bromide [161] and poly (ethylene glycol) PEG - 6000 [165] are reasonably consistent with those of the binary NajCit + Hp systems when the vapour-pressure lowerings Ap(7 /w) are considered (Fig. 5.7). However, the agreement when expressed in terms of osmotic coefficients iT m), as will discussed later, is less satisfactoiy. Actually, all reported... 

Several authors have shown a general increase in the capacity of poly-oxyethylated non-ionic surfactants to solubilize water with increase in the length of the oxyethylene chain [209,210]. Fig. 5.30 shows the vapour pressure of water in 0.5 % solutions of a series of dodecyl polyoxyethylene glycols in tetrachlor-ethylene plotted as a function of the water content of the system. The decrease in... 

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