Hetero-azeotrope

This ensures liquid-liquid equilibrium. Trivial solutions whereby x = xf need to be avoided. The results are shown in Figure 4.8 to be x[ = 0.59, xf = 0.98. The system forms a hetero azeotrope. 

Water and n-butanol in the concentration range of about 50-98.1 mol % water form two liquid phases that boil at 92.7°C at one atm. On cooling to 40°C, the hetero-azeotrope separates into phases containing 53 and 98 mol % water. 

Simple distillation cannot separate aromatics from noD -aromatic, because the relative volatilities are very low, and many azeotropes are formed. Azeotropic distillation is based on the formation of an azeotrope betu een the non-aromatic hydrocarbons and a low boiling polar solveat It is select among the hrst terms of the series of alcohols, ketones, aldehydes and nitriles, and is employed pure or mixed with water. If the solvent forms a hetero-azeotrope, its recovery is accordbgly facilitated. The )aeld is not limited in principle. The impurity content of the feedstock and the composition of the azeotrope determine the amount of solvent required. Cuts rich in aromatics can be treated in this way fairly economically. However, any variation in the type of impurity to be removed, and consequently in the composition of the azeotrope, may lead to less perfect purification. Furthermore, this method can be applied only to a narrow cut which contains... 

New Configuration For Hetero-Azeotropic Batch Distillation I. Feasibility Studies... 

A number of differences nevertheless appear between the purification schemes of acetone and methyl ethyl ketone. The existence of a water/methyl ethyl ketone hetero-azeotrope (bpi.o 73.4°C, water content 11.3 percent weight) complicates the separation of the products. 

In these units the solvent in the extract draining out of the extractor is distilled off, condensed, and recycled to the extractor. The distillation provides both concentrated extract and flesh solvent feed. If the solid is moist and a nonaqueous solvent is used, water will codtstill with the solvent. If the water-rich portions of the (Sstillate are replaced with fresh solvent and not recycled to the bed, the solid will dry as leaching proceeds. The amount of solvent replacement required can be minimized if the solvent and water form a hetero azeotrope. 

Swi toslawski s ebullio-meter, as modified by Olszewski, for hetero-azeotropic mixtures... 

In a case of azeotropic distillation an additional component is introduced that forms a lower boiling binary or ternary azeotrope (e.g. a hetero-azeotrope), which is easier to separate than the original azeotrope. 

However, the number of phases is not limited to two only. For example, in the case of hetero-azeotropic mixtures like butanol-water or ethanol-water-cyclohexane already two liquid phases exist besides the vapor phase. Hildebrand showed that in the system water-heptane-perfluorokerosene-aniline-phosphorus-gallium-mercury even seven liquid phases are in equilibrium with the vapor phase [2] (see Figure 5.3). 

Formation of a Ic. v boiling binary or ternary (hetero-) azeotrope... 

It follows from this that Bernoulli and Markov mechanisms differ in whether the transition probabilities of the crossover, or hetero, steps are the same as or different from the homo steps (see Table 15-6). In addition, both types of mechanism can be subclassified as to whether the transition probabilities for the homo linkages are symmetric or asymmetric. In copolymerization, a symmetric Bernoulli mechanism with constitutionally different monomers is called azeotropic copolymerization with configurationally different monomers, it is called random flight polymerization and in stereocontrolled polymerization with nonchiral monomers, it is also called ideal atactic polymerization. ... 

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