Hydrocarbons binary azeotropes with

Isoprene [78-79-5] (2-methyl-1,3-butadiene) is a colorless, volatile Hquid that is soluble in most hydrocarbons but is practically insoluble in water. Isoprene forms binary azeotropes with water, methanol, methylamine, acetonitrile, methyl formate, bromoethane, ethyl alcohol, methyl sulfide, acetone, propylene oxide, ethyl formate, isopropyl nitrate, methyla1 (dimethoxymethane), ethyl ether, and / -pentane. Ternary azeotropes form with water—acetone, water—acetonitrile, and methyl formate—ethyl bromide (8). Typical properties of isoprene are Hsted in Table 1. 

One hydrocarbon reaction product produced by Celanese contains over forty components which are capable of forming more than fifty binary azeotropes with each other.17 Several ternary azeotropes are also known to exist. Azeotropes of eleven of the oxidation products are listed in Table 6-2. An examination of Table 6-2 shows that the separation of any one product from the mixture of eleven components would be most difficult to effect by straight fractionation. 

Liquid with pungent odor. bp7 81.4. tig 1.4086. dj 0.8636 dj5 0 8407. Easily soluble in water, methanol, ethanol, ether, acetone, glacial acetic acid. Slightly sol in hydrocarbons. Forms a binary azeotrope with water, bp 75 (12% water), uv spectrum and electric moments Rogers, J. Am. Chem. Soc. 69, 2544 (1947). Polymerizes on standing, LDm in mioe and rats 35 mg/kg, C.A. 72, 124809b 0970). 

Esters of low volatility are accesible via several types of esterification. In the case of esters of butyl and amyl alcohols, water is removed as a binary azeotropic mixture with the alcohol. To produce esters of the lower alcohols (methyl, ethyl, propyl), it may be necessary to add a hydrocarbon such as benzene or toluene to increase the amount of distilled water. With high boiling alcohols, ie, benzyl, furfuryl, and P-phenylethyl, an accessory azeotroping Hquid is useful to eliminate the water by distillation. 

Based on the above information, the CAMD problem definition is revised as follows - The solvent can be acyclic hydrocarbons and ketones (aromatic compounds, chlorides, dioxanes are not considered for EH S concerns). The normal boiling point should be higher than that of chloroform (334 K), the molecular weight could be between 70-120, the solvent must not form azeotrope with either acetone or chloroform, and, must be totally miscible with the binary mixture of acetone and chloroform. 

Such a process depends upon the difference in departure from ideally between the solvent and the components of the binary mixture to be separated. In the example given, both toluene and isooctane separately form nonideal liquid solutions with phenol, but the extent of the nonideality with isooctane is greater than that with toluene. When all three substances are present, therefore, the toluene and isooctane themselves behave as a nonideal mixture and then-relative volatility becomes high. Considerations of this sort form the basis for the choice of an extractive-distillation solvent. If, for example, a mixture of acetone (bp = 56.4 C) and methanol (bp = 64.7°Q, which form a binary azeotrope, were to be separated by extractive distillation, a suitable solvent could probably be chosen from the group of aliphatic alcohols. Butanol (bp = 117.8 Q, since it is a member of the same homologous series but not far removed, forms substantially ideal solutions with methanol, which are themselves readily separated. It will form solutions of positive deviation from ideality with acetone, however, and the acetone-methanol vapor-liquid equilibria will therefore be substantially altered in ternary mixtures. If butanol forms no azeotrope with acetone, and if it alters the vapor-liquid equilibrium of acetone-methanol sufficiently to destroy the azeotrope in this system, it will serve as an extractive-distillation solvent. When both substances of the binary mixture to be separated are themselves chemically very similar, a solvent of an entirely different chemical nature will be necessary. Acetone and furfural, for example, are useful as extractive-distillation solvents for separating the hydrocarbons butene-2 and a-butane. 

MICHEAU - My comments deals with azeotropic binary mixtures. We have recently made some experimental measurements of the thermodynamic parameters of a thermochronic equilibrium in azeotropic liquid mixtures. Our thermochronic equilibrium (Nickel complexes NiR + 2S N1R2S2) is sensitive to the donor number of the solvent S which is an empirical measure of the availability of the electronic doublet of S. What we have found in azeotropic mixtures (alcohol + halogenated hydrocarbons) is that near the room temperature there is a kind of natural compensation of the alcohol doublet availability by the presence of halogenated hydrocarbons molecules this compensation shifts the equilibrium position near 50/50 (solvated vs non solvated complex). This property is spontaneous with the azeotropes we have studied, but must to be adjusted accurately by varying the molar ratio with similar binary mixtures not giving azeotropes. So, it appears that azeotropes exhibit from this point of view some singular propertie. My question is Do you have or do you know some results about reactivity studies in azeotropic mixtures Could an azeotrope be considered as a model of a particular supermolecule or cluster ... 

As an example of such an operation, consider the process of Fig. 9.54, The separation of toluene (bp 110.8 C) from paraffin hydrocarbons of approximately the same molecular weight is either very difficult or impossible, due to low relative volatility or azeotropism, yet such a separation is necessary in the recovery of toluene from certain petroleum hydrocarbon mixtures. Using isooctane (bp = 99.3°C) as an example of a paraffin hydrocarbon, Fig. 9.54a shows that isooctane in this mixture is the more volatile, but the separation is obviously difficult. In the presence of phenol (bp = 181.4 C), however, the isooctane relative volatility increases, so that, with as much as 83 mole percent phenol in the liquid, the separation from toluene is relatively easy. A flowsheet for accomplishing this is shown in Fig. 9.546, where the binary mixture is introduced more or less centrally into the extractive distillation tower (1), and phenol as the solvent is introduced near the top so as to be present in high concentration upon most of the trays in the tower. Under these conditions isooctane is readily distilled as an overhead product, while toluene and phenol are removed as a residue. Although phenol is relatively high-boiling, its vapor pressure is nevertheless sufficient for its appearance in the overhead product to be prevented. The solvent-recovery section of the tower, which may be relatively short, serves to separate the phenol from the isooctane. The residue from the tower must be rectified in the auxiliary tower (2) to separate toluene from the phenol, which is recycled, but this is a relatively easy separation. In practice, the paraffin hydrocarbon is a mixture rather than the pure substance isooctane, but the principle of the operation remains the same. 

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