Azeotropic distillation methyl ethyl ketone

An even more advantageous condition exists in the case of the toluene range hydrocarbons when methyl ethyl ketone and water are added. A ternary azeotrope of methyl ethyl ketone-water-nonaromatic hydrocarbons distills below 176° F. Neither methyl ethyl ketone nor methyl ethyl ketone-water forms an azeotrope with toluene hence, toluene will not distill until a temperature of 231 ° F. is reached, unless excess water is present. Thus, it is relatively easy to produce pure toluene from petroleum fractions ... 

As stated in Chapter 7, the composition of an azeotrope varies with the distillation pressure. Thus, the azeotrope between ethanol and water contains 89.4 mol% ethanol at atmospheric pressure, 90.2 mol% ethanol at 380 mm Hg, and 92.0 mol% ethanol at 190 mm Hg absolute pressure [6]. Similarly, the azeotrope between methyl ethyl ketone and water contains 65.4 mol% MEKat atmospheric pressure, 70.0 mol% MEKat 350 mm Hg, and 72.2 mol% MEKat 200 mm Hg absolute pressure. Because MEK and water form two immiscible liquid phases upon condensation of the overhead, these two compounds can be separated by distilling each of these two phases separately. Because the azeotrope of ethanol and water is a single-phase liquid, separation of these two components can be achieved by distillation in two columns operating at different pressures in order to shift the azeotropic composition. 

When azeotropic distillation is used for toluene, the solvent used is usually a mixture of methyl ethyl ketone (MEK) and water (10%). The solvent and the toluene are mixed, heated, and then charged to a distillation column... 

Fig. 2. Methyl ethyl ketone (MEK)—methyl isopropyl ketone (MIPK)—water system where A1 and A2 represent two different azeotropes FI, F2, and F3, different feed compositions Bn and Dn the corresponding bottoms and distillates, respectively (—-), the distillation boundary and ( ), the reachable compositions for the various feeds (a) approximate bow-tie and (b) exact reachable compositions.

Azeotropic Distillation. The concept of azeotropic distillation is not new. The use of benzene to dehydrate ethyl alcohol and butyl acetate to dehydrate acetic acid has been in commercial operation for many years. However, it was only during World War II that entrainers other than steam were used by the petroleum industry. Two azeotropic processes for the segregation of toluene from refinery streams were developed and placed in operation. One used methyl ethyl ketone and water as the azeo-troping agent (81) the other employed methanol (1). 

Another example presented by Hopkins and Fritsch17 consists of the use of azeotropic and extractive distillation to recover part of the methyl ethyl ketone... 

The geometric properties of a RCM allow its simple sketch. Figure 9.5 shows the construction for the mixture methyl-isopropyl-ketone (MIPK), methyl-ethyl-ketone (MEK) and water. Firstly, the position of the binary azeotropes and of the ternary azeotrope is located. Then the boiling points for pure components and azeotropes are noted (Fig. 9.5a). The behaviour of characteristic points (node or saddle) is determined by taking into account the direction of temperatures. Finally, straight distillation boundaries are drawn by connecting saddles with the corresponding nodes (Fig. 9.5b). 

Azeotropic distillation is only of minor importance in the production of BTX aromatics the most important azeotropic entrainers are methyl ethyl ketone and methanol. Figure 4.13 shows the production of toluene by azeotropic distillation with methanol. 

A simpler large scale method to obtain pyrantel, morantel (10a,b) and oxantel (11) involves condensation of 23 with an aryl aldehyde in presence of a base. Water is removed by azeotropic distillation or by using a chemical scavenger like methyl/ethyl formate, which reacts with water to push the reaction in the forward direction (Scheme 3). Other methods to prepare pyrantel and its derivatives are also reported [5,6,13-17]. The l-(2-arylvinyl)pyridium salts (18,19), structural congeners of pyrantel/moratel, are prepared by quaternisation of pyridine with the appropriate bromomethylaryl ketones (27) to afford 28. The latter is reduced with sodium boro-hydride to give the carbinol 29, which on dehydration leads to the formation of l-(2-arylvinyl)pyridinium bromides (18,19) [8]. 

Efficient enzymatic conversion can be achieved even though most of the reactants are present as solids, provided that there is a liquid phase in which the reaction can occur. This approach has been successfully used for carbohydrate ester synthesis with synthesis of glucose esters of fatty acids between C12 and C18 as typical examples [34]. It is important that the substrates dissolve during the reaction, and often the products precipitate as they are formed, which can be an advantage due to a favourable effect on the equilibrium position. Candida antarctica lipase B is an efficient catalyst in this system and solvents used (in moderate amounts) include ethyl methyl ketone, acetone or dioxane. In order to increase the ester yield, water formed in the reaction can be removed by azeotropic distillation and the solvent (e.g. ethyl metyl ketone) can after condensation be dried by pervaporation, giving a practically useful complete process [35]. 

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