Water-immisdble solvent

Mixtures of triglycerides, triglycerides plus free fatty adds or triglycerides plus fatty acid alkyl esters are used as reactants in fat modification processes. These mixtures are exposed to lipases supported on macroporous particles in the presence of a small amount of water. Liquid substrates (oils) can be reacted without use of a solvent, but with solid reactants (fats) it is necessary to add a solvent to ensure that the reactants and products are completely dissolved in the organic phase. Various water immisdble solvents can be used, but hexane is preferred for commercial operation because this solvent is already used industrially for the processing of oils and fats. 

In a two-phase systent (Figure 25c), the organic (water immisdble) solvent may be used as product extractant. In addition, recirculation of the organic phase can serve to transfer oxygen and to mix the aqueous phase. 

The reaction systems used for modification of triglycerides usually consist of a lipase catalyst and a smaU amount of water dispersed in a bulk organic phase containing the reactants and, if required, a water immisdble solvent The sinall amount of water in the reaction system pa ticms between the catalyst and the bulk organic phase. 

The solubility characteristics of any given compound will uniquely govern that substance s distribution (partition) between the phases of two immiscible solvents (in which the material has been dissolved) when these phases are intimately mixed. In this experiment we determine the partition coefficient (distribution coefficient) of benzoic add between two immisdble solvents, methylene chloride and water. 

Given the mle of thumb in Chapter 4.16.5, one shotfld expect to manage a "flood" of liquid water contaminating the water-immisdble (normally) liquid cleaning solvent after its removal from the adsorbent bed. 

Organic aqueous two-phase solvent systems are also widely applied for other biotransformations, for example, in hydrolase-catalyzed processes [37,49]. A typical example is the enantioselective hydrolysis of a racemic, water-immisdble ester as a substrate. The reaction yields a water-soluble carboxylic acid (in depro-tonated form as a salt). Ionic liquids have also been used in biphasic systems, a topic that is discussed in detail in Chapter 3 in this book [50]. 

As is the case for organic solvents, several workers have investigated two-phase systems in which water-immisdble ionic liquids are mixed vdth aqueous buffers. Such strategies offer all of the advantages of organic/aqueous biphasic mixtures, but without the drawbacks of handling volatile and flammable solvents. Some examples are shown in this section. 

The oxime is obtained by the action of hydroxylamine hydrogen sulfate on cydododecanone. This operation takes place in a solvent that is immisdble with water or with concentrated sulfuric add, which are used in the next step. The most widely used solvent is isopropylcydohexane (or hydrocumene) which dissolves the oxime at the reaction temperature of 100 G Conversion is practically quantitative. It takes place in a series of reactors equipped with effective agitators, into which aqueous solutions of hydroxyl-amine sulfate are introduced, together with ammonia to keep the pH about 7. The effluent is cooled aad settled. The aqueous layer containing ammonium Sulfate is removed. The organic phase is washed with concentrated sulfuric add. The oxime sulfate solution... 

Solvent injection is usually followed by the injection of a cheaper drive fluid. The solvent slug may be displaced misdbly with another gas, for example, natural or flue gas, or immisdbly with water. 

To understand the most fundamental concept of Uquid-liquid extraction, consider placing 100 mL of an aqueous solution that contains O.IM NaCl and O.IM acetic add, HO Ac, into a piece of laboratory glassware known as a separatory or commonly abbreviated as a sep funnel (2). This is depicted in Figure 3.1A. Next, 100 mL of diethyl ether, amoderately polar organic solvent that is largely immisdble with water, is added to the funnel. Indeed, some ether will dissolve in water to the extent of 6.89% at 20°C while some water dissolves in the ether to the extent of 1.26% at 20°C (3). 

The aim of this chapter was to provide a comprehensive review of the type of water sorption and solvent sorption behavior that can be expected from miscible or immisdble, but compatible, polymer blends. It was concluded that miscibility depends on the molecular stmctures of the polymers, their morphologies and the blend composition, as well as the processes of the blends. Several blends also exist which, despite intermolecular hydrogen bonding, do not form thermodynamically homogeneous blends due to the stiffness and self-association of the polymer chains. 

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