Mixtures, azeotropic completely miscible

Phenol has a low melting point, it crystallizes in colourless prisms and has a characteristic, slightly pungent odor. In the molten state, it is a clear, colourless, mobile liquid. In the temperature range T < 68.4 °C, its miscibility with water is limited above this temperature it is completely miscible. The melting and sohdification points of phenol are quite substantially lowered by water. A mixture of phenol and ca 10% water is called phenolum liquefactum, because it is actually a liquid at room temperature. Phenol is readily soluble in most organic solvents (aromatic hydrocarbons, alcohols, ketones, ethers, acids, halo-genated hydrocarbons etc.) and somewhat less soluble in aliphatic hydrocarbons. Phenol forms azeotropic mixtures with water and other substances. 

Tetrahydrofuran [109-99-9] (oxolane, tetramethylene oxide, oxacyclopentane, THE) [14.271] is a colorless, highly volatile liquid having an outstanding solvency. Under prolonged exposure to air it tends to form peroxides. Tetrahydrofuran is completely miscible with most organic solvents and water. It forms azeotropic mixtures with a number of solvents. Tetrahydrofuran dissolves practically all plastics apart from certain polyamides (e.g., polyamide 6 and 12) and polytetrafluo-roethylene. 

The property of butyl Cellosolve most often used in its recovery is its water solubility, and its behaviour in water mixtures is therefore of great importance. As Fig. 16.13 shows, butyl Cellosolve is completely miscible with water at low temperatures but forms two liquid phases at certain concentrations above 57 °C. Its UCST is 128 °C. At the boiling point of the butyl Cellosolve/water azeotrope the condensate splits into an aqueous phase containing about 2% and an organic phase of about 57% w/w (0.17 mole fraction) of butyl Cellosolve. The organic phase can very easily be separated by distillation into the azeotrope and a dry butyl Cellosolve fraction. 

The location of the azeotropic point depends on pressure, its position in the equilibrium diagram shifts to the right with a decrease in pressure. A higher fraction of more volatile component is then found in the azeotropic mixture. The separation of such a liquid mixture by distillation is based on this fact. Components are completely miscible and form a minimum or maximum azeotrope without a third component. 

Ethanol has also been utilized for oil extraction. Oil solubility in ethanol varies with temperature and water content. Soybean oil is completely miscible with absolute ethanol above 70 °C (Johnson and Lusas, 1983). As ethanol concentration decreases and water content increases, oil solubility is significantly reduced in the mixture. The higher cost and latent heat of vaporization are the major disadvantages of ethanol as a solvent for oilseed extraction. Recent developments in bioethanol production may reduce the cost of ethanol, making it a viable alternative to hexane. Solvent mixtures can also be used to extract oil. Hexane/alcohol azeotropes have been used for extraction of residual lipids from hexane-extracted meals to improve flavor and odor, specifically from soybean and peanuts. Grassy and beany flavors in oilseeds are associated with the presence of phosphatides, which can be easily extracted with hexane/alcohol mixtures. Similarly, hexane/alcohol azeotropes, specifically hexane/methanol, are very effective in extracting aflatoxin from meal. 

The condensate that collects on the cold surface is usually a completely homogeneous, or miscible, mixture of components. In general, the relative composition of the liquid components in the condensate is different from the composition in the vapor phase (except for an azeotropic mixture, where the condensate has the same exact molar concentration ratio as the vapor phase) [194]. The film that forms is not necessarily smooth but may show the appearance of streamers (or rivulets), waves, or droplets, depending on the particular mixture and its surface tension (which depends on the local wall temperature) [25,195,196]. If the condensate mixture is heterogeneous, or immiscible (as can occur when one component, for example, is aqueous and the other is organic), the pattern can be quite complex, looking somewhat like dropwise condensation [25,193,197]. These different condensate patterns affect the resulting fluid flow and heat transfer. 

According to Gibbs phase rule a completely soluble binary mixture is enriched in both phases, whilst an immiscible binary mixture, with its three phases, cannot be enriched (see Fig. 29, a—d). It wiU be recognized, on the other hand, that three-component systems having a miscibility gap, f.e. showing two liquid phases and one vapour phase, are separable by countercurrent distillation [1]. A typical example is the preparation of absolute alcohol by azeotropic distillation with benzene. 

Processes for completely fractionating binary mixtures with heteroazeotropes consist of two distillation columns and one decanter (Fig. 11.3-1). As the azeotrope lies within the miscibility gap of the liqnid the azeotrope can be broken by decantation. The two fractions from the decanter are at different sides of the azeotropic point. Purification of these two rather impnre fractions is performed by distillation. The pure products are recovered as bottoms from the distillation columns C-1 and C-2. 

Based on the above results, the reuse of 3,5-(CioF2i)2C6H3B(OH)2 has been examined for the direct amide condensation reaction of cyclohexanecarboxylic acid and benzylamine in a 1 1 1 mixture of o-xylene, toluene, and perfluorodecalin under azeotropic reflux conditions with removal of water for 12 h (Table 10.2 and Figure 10.1). Perfluorodecalin is not miscible with a non-fluorous solvent, toluene or o-xylene, even under reflux conditions. After completion of the reaction, the homogeneous solution is cooled to ambient temperature and separated in the bi-phase mode... 

Ethanol is a monohydric primary alcohol. It melts at -117.3°C and boils at 78.5°C. It is miscible (i.e., mixes without separation) with water in all proportions and is separated from water only with difficulty ethanol that is completely free of water is called absolute ethanol. Ethanol forms a constant-boiling mixture, or azeotrope, with water that contains 95% ethanol and 5% water and that boils at 78.15°C since the boiling point of this binary azeotrope is below that of pure ethanol, absolute ethanol caimot be obtained by simple distillation. However, if benzene is added to 95% ethanol, a ternary azeotrope of benzene, ethanol, and water, with boiling point 64.9°C, can form since the proportion of water to ethanol in this azeotrope is greater than that in 95% ethanol, the water can be removed from 95% ethanol by adding benzene and distilling off this azeotrope. Because small amounts of benzene may remain, absolute ethanol prepared by this process is poisonous. 

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